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AGELLATA.

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PROTOCOL-PROVOST

undeveloped conditions of Algo; also known as Chlorophyllo-
phyceae, and often placed as a series of Chlorophyceae or green
Algae.

Protocol. Original draft of any document, as a treaty;
minutes of diplomatic proceedings.

Protodont Dentition. Molar teeth of mammals, whose crowns are compressed and fitted for cutting, rudimentary tubercles being developed on the edges of a main tubercle. The loss of these accessory serrations converts the tooth into the haplodont type.

Protogenes, 4th cent. B.C. Greek painter of Caria, active at Rhodes.

Protogenesis. In Biology, propagation by budding. Protogenic. In Plant Anatomy, intercellular spaces in plants which are formed coincidently with the growth of surrounding tissues.

Protohydra. See ARCHEGASTRULA.

Protonema. First filamentous growth from the germinating spore of the mosses, on which the moss-plant is subsequently developed from a lateral bud.

Protophyta. Sub-kingdom of plants, including the smallest and simplest members of the vegetable kingdom; usually restricted to those whose increase is effected only by vegetative propagation.

Protoplasm (BIOPLASM). Jelly-like substance contained
in the cambium cells of plants: so named by von Mohl 1846;
identified 1863 with the Dujardin's Sarcode, 1835, of animal
tissues. In it inheres the essential characteristics of living
things; viz., irritability, contractility, assimilation, reproduc-
tion. heredity, variability or adaptability to environment, etc.
To manifest these properties of life it requires an environment
containing moisture, a temperature between 32° and 110° F.,
and organic food compounds of considerable complexity, though
if chlorophyl be present it can utilize water and carbonic acid
by absorbing the energy of light. Protoplasm consists of va-
rious highly complex proteids, built up into a complicated
mechanism of unknown structure, but of which we have some
glimpses in the phenomena of KARYOKINESIS (q.v.).

Protoplast. Plant or animal cell in its simplest form.
Protopodite. Basal or proximal portion of the append-
ages of a Crustacean. It consists of two joints, a proximal
coxopodite and a distal basipodite.
branches, endopodite and exopodite.
The latter bears two
Protopteri. See DIPNOI.

Protopterus. See DIPNEUMONA.

Prototheria (AMASTA, ORNITHODELPHIA, MONOTREMATA). Sub-class of non-placental Mammalia, including the single order Monotremata. The jaws are toothless in the adult, and sheathed with a beak. Marsupial bones (and pouch) are present. There is a large coracoid. The reproductive organs are bird-like; the testes remain in the body cavity; a cloaca is present, and meroblastic eggs are laid. Two genera are included, ORNITHORHYNCHUS and ECHIDNA (q.v.).

Prototracheata. See ONYCHOPHORA.

Protozoa. First animals, and lowest in scale of organization. They are single cells or colonies of similar cells, and reproduction takes place by cell-division or by spore formation, sometimes preceded by conjugation or by copulation. They are divided into Rhizopods and Infusoria, or more broadly into Gymnomyxa and Corticata. The group includes most of the animalcules.

Protractor. Circular or semi-circular sheet of paper or metal, graduated along its edge, and used for plotting angles.

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Proud, JOSEPH, 1745-1826. of above 300 hymns, of which 164 are used by the New Ch English Swedenborgian, a Proud, ROBERT, 1728-1813. Historian of Pa. 1797-98. Proud Flesh. Granulations of an inflamed wound. form part of the process of repair and only when exce should they be interfered with.

Proudhon, PIERRE JOSEPH, 1809-1865. French soci repeatedly fined, imprisoned, or exiled for his publicat Sociale, 1852. Qu'est-ce que la Proprieté? 1840; Contradictions Economi 1846; Confessions d'un Révolutionnaire, 1849; La Révol

Pro-ungulata. See UNGULATA.

Proust, JOSÈPHE LOUIS, 1755-1826. French chemist; tea
in Spain. Essai d'une Statique Chimique, 1803.
Proustite. 3Ag,S+As,S,. Light red silver ore cont
ing 65.5 per cent silver when pure.
Mexico, and Idaho.
It occurs at Freib

Prout, FATHER. See MAHONY, F.
Provençal.

Romance dialect of s. France, the lan d'oc and tongue of the troubadours, flourishing as a liter language chiefly ab.1100-1300.

Provence. Former French province, on the Mediterrane famous in the Middle Ages; absorbed 1481. It was overrun

[graphic]

Ruins in Provence.

the 5th century by the Visigoths and Burgundians, and wa under the Saracens later. It contains many ruins.

Proventriculus. 2. Dilatation of the oesophagus of birds in front of the gizzard tween the crop and the chylific ventricle of certain insects 1. Masticatory stomach inserted be 3. Similar expansion in front of the stomach in frogs, etc. Proverbs. Brief, pithy sayings, "sententious and true long since accepted as such by common consent"; "shor sentences drawn from long experience"; "the wisdom of many and the wit of one." They are found among all nations, and have been collected by many hands, as by Erasmus, 1500. Proverbs, BOOK OF. utterances as to the conduct of life, prefaced by nine chapters 20th O. T. book; collection of gnomic of admonitory poetry. rising in ch. viii. to high religious sublimity; ascribed to Solomon, with appendices by Agur and others.

Providence. Deity, not as first cause, but as present cause interfering to regulate the lot and condition of his creatures in their own behalf.

gansett Bay; seat of Brown Univ. Its coast wise commerce is Providence. Chief city of R. I., at the head of Narraextensive, but the principal industry is manufactures, especially of cotton and woolen goods, iron and steel, and jewelry. It was settled 1636 by Roger Williams, and chartered as a city 1832. Pop., 1890, 132,146.

Provincial. Monastic superior, who, besides his own house, has appellate authority over all the houses of his order within a certain district.

Proving-Ground. Establishment for the proving of ordnance before it is finally issued for service. At Sandy Hook, N. J.. all the heavy guns, carriages, and rapid-fire guns for service in the U. S. Army are proved, and experimental tests are there made upon trial pieces of ordnance, by ordnance officers under the direction of the Chief of Ordnance. Provocation, IN ETHICS. Such degree of inducement to a crime as mitigates the offense.

chaplain of Congress 1785.
Provoost, SAMUEL, D.D., 1742-1815. Bp. of N. Y. 1787;

Provost. Dignitary at the head of a college chusel

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PROVOST-MARSHAL-PSALM

Provost-Marshal. Commissioned officer of the army, appointed by the commanding officer to superintend the preservation of order and to act as the chief of police of the camp He possesses summary power to or army during time of war. punish offenders, has charge of the guard and prisoners, and regulates the conduct of camp-followers.

Proxy. Authorization to act for another, as in voting, and he who exercises it.

Proxylem. In Plant Anatomy, first-formed xylem cells in a fibro-vascular bundle.

Prudden, THEOPHILE MITCHELL, M.D., b. 1849. Prof. College of Physicians and Surgeons New York 1892; writer on pathology. Histology, 1881; Bacteria, 1889; Dust, 1891. Prudence. Intellectual virtue by which we select the right means to a given end, assumed to be the proper object

of action.

Spanish Prudentius, AURELIUS CLEMENS, 348-ab.413. Christian poet; lawyer, judge, and ab.394 official at Rome. His hymns (Cathemerinon and Peristephanon) and other works, mostly doctrinal and controversial, are all in Latin verse, and were produced probably after 405.

Prud'hon, PIERRE PAUL, 1758-1823.

French historical

and portrait painter. At Rome he met Canova, which influ

In

they founded cities, introduced German colonists, laws,
civilization. In 1454 the municipal and noble classes, aided
Poland, rebelled. The knights, by treaty of Thorn 1466, ce
territory to Poland, retaining part in fealty to her.
the Markgraf, Albert of Anspach and Baireuth, a Hohen
lern, was chosen Grandmaster, and was acknowledged as D
of P. 1525. Johann Sigismund, elector of Brandenburg,
founder of the Hohenzollern-Brandenburg house 1609.

The territory between the Elbe and Oder, which had longed from the 12th century to descendants of Albert Bear, now fell in. The whole country was soon desolated the Thirty Years' War, but its finances were restored by Great Elector, Frederic William; and under Frederic II., added Silesia, its prestige reached a high point. Further ditions of territory resulted from the partitions of Pol conflict with Napoleon, was defeated 1806, and lost most o Frederic William III., having left his neutral position in territory. Reorganization of the army, educational and s measures, restored the strength of the nation, which j the Allies 1813 in their struggle against France. The der After the revolution of for a constitution, promised 1815, was followed by effor check the growth of liberalism.

some conciliatory measures were taken, and plans to
mote German unity were welcomed. The Schleswig-Ho
troubles resulted, 1866, in a victorious war of 6 weeks
Austria; the states n. of the Main were partly annexed
partly joined with her in the N. German Confederation; S
A str
wig-Holstein was also annexed. War with France, 1870-
which P. was joined by the rest of Germany, ended in th
onation of William I. as emperor of Germany.
with the papal power followed. The guiding spirit in
events was Prince Bismarck. The present period is mark
the growth of Socialism. Pop., 1890, 29,957,367.

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The

Prussian Blue. Various forms are known.
common is the blue insoluble powder, Fe, (Fe(CN)), F
FERROCYANIDE (q. v.), prepared by mixing ferric solution
a solution of yellow prussiate of potash. It is used as a pig
Prussian Language, OLD. See LETTISH.
Prussic Acid. See HYDROCYANIC ACID.
Prutenic Tables. Astronomical tables, based
system of Copernicus, and corrected by Brahe.

River in s.e. Europe, Austria, Roumani
Pruth.
Russia, rising in Austrian Bukovina, flowing e. and s..

f

[graphic]

Cupid Caressing before Wounding, by Prud'hon.
enced his style. He forms an interesting figure in French art.
His pictures have a grace and tenderness which is wanting in
all the pictures of his contemporaries.

Pruinose. Surfaces of fruits or other organs when cov-
ered with a bloom.

Prune. Dried fruits of certain varieties of the cultivated plum.

Prunella. Thin woolen or mixed stuff, formerly used for clergymen's gowns, but now employed for covering shoes.

Pruning. Cutting off the branches of trees or shrubs, for
the purpose of improving the fruit or timber. Early spring or
late winter is the best time for pruning.

At present it
Prurigo. Skin disease attended with intense itching (pru-
ritus). Like so many of the terms employed by dermatolo-
gists, it is used variously by different authors.
is most commonly applied to a chronic, almost incurable, dis-
ease beginning early in life and accompanied by an eruption
closely resembling the hives (urticaria).

Prussia. Largest and most important state of Germany.
It is mainly a plain, being mountainous only in the s. part.
Its area is 136,075 sq. m. The culture of rye, the beet root,
and the vine, with the raising of cattle, constitute the princi-
pal occupation of the rural population. Manufactures are ex-
tensively carried on and are varied. The mineral resources
are great, and the state has a large internal and external com-
The government is a limited monarchy, the king of
P. being emperor of Germany. The capital is Berlin. The Sla-
vonic tribes that early occupied the Baltic shore were known
Boleslas of Poland
in the 10th century as Borussi. Bishop Adalbert of Prague
suffered martyrdom among them 997.
bebantized 1018, but they rebelled 1161. Their
led the crusade of the

merce.

try:

Banks of the Pruth.

the frontier between Roumania and Russia and join Danube at Reni. Length 380 m.

Prutz, ROBERT EDUARD, 1816-1872. Prof. Halle poet, dramatist, critic, and historian of German jo and the stage.

English controv Prynne, WILLIAM, 1600-1669. Cromwell 1650-52; M.P. 1648 and 1658; keeper of reco Tower 1660. imprisoned 1634-40 for his Histrio-mastix, 1633; twice pilloried, and cropped; branded in both cheeks 1627;

Pryor, ROGER ATKINSON, LL.D., b. 1828. M.C. 1859-60; Brig.-gen. C.S.A. 1863; prominent at New from 1865; Judge of Common Pleas 1891, and of N. Y. Court 1896.

Prytanis. Greek magisterial title, whose meani in different cities. At Rhodes they were the supren trates, while at Athens the fifty prytanes, for the ti represented a tribe and presided at the meetings of th of five hundred. They held office for a tenth of a y another tribe assumed the office. These officers in Gr had certain religious functions, as the care of the sac the prytaneum, from which the hearth of a new col be lighted.

Psalm. Hymn, or sacred song, the prevailing being of thanksgiving and praise, sung to the accon of a harp or similar stringed instrument and consti principal liturgical element in the Hebrew temp

colonists, laws, and oble classes, aided by of Thorn 1466, ced alty to her. In 1 aireuth, a Hobetaknowledged as Dare of Brandenburg, house 1609. Oder, which had ndants of Albert as soon desolated fr were restored by th nder Frederic IL, #bo h point. Further &partitions of Polat eutral position in te 6. and lost most of Li educational and sor nation, which je France. The demar followed by efforts to the revolution of 19 en, and plans to pr The Schleswig-Holsten swar of 6 weeks w e partly annexed to. Confederation: Sellis with France, 1870-71 many, ended in the c Germany. A stra guiding spirit in thev Sent period is marked s 29,957.367.

are known. The s er, Fe,(Fe(CN),),, FERDY king ferric solutions m. It is used as a piguet

- LETTISH.

IC ACID. cal tables, based on by Brahe.

Austria, Roumacia 2. flowing e, and s., farm

Pruth.

nd Russia and joining -1872. Prof. Halle 1 rian of German jouras

- English controversias -mastix, 1633; twice fo both cheeks 167: J 1658; keeper of reconsin

.D., b. 1828. M.C. frem prominent at New Ex. as 1891, and of N. Y. S

l title, whose meaning hey were the supren

prytanes, for the time at the meetings of the ce for a tenth of a yea These officers in Greci as the care of the sacred

hearth of a new const

ong, the prevailing s
e, sung to the accompan
and constit

PSALMANAZAR--PSILOTEÆ

David was plainly a composer and regulator of the Temple
service as well as a poet. The Psalms were carried over into
the Christian service in the form of unisonous antiphonal song,
and were among the first of the sacred texts to be utilized by
the composers when artistic music entered the church.

Psalmanazar, GEORGE, ab. 1680-1763. Impostor, of un-
known origin, whose Description of Formosa, 1704, deceived
the English for some years. He confessed, amended his ways,
wrote other books, and was highly esteemed by Dr. Johnson.
Psalmody. Singing of psalms, either by Jews or Chris-
tians; hence the study and translation of them, with all that
relates to the accompanying tunes.
those of Sternhold and Hopkins, 1549-62, and Tate and Brady,
Versions of psalms, chiefly
1696, were almost exclusively used in English worship till after
1700, and formed the chief metrical provision till long after
1800. In Germany and other Protestant lands hymns came
into use much earlier.

Psalms. 19th O. T. book (subdivided by the Hebrews into
five), containing 150 religious odes, of varying poetic excellence
and spiritual depth, ranging in date of composition perhaps
from 1000 to 150 B.C.; 73 are doubtfully credited to King
David, and 12 to Asaph.

Psalterium. Manyplies, or third pouch of the ruminant stomach. Its walls are deeply folded into longitudinal septa. It receives the food after it has been chewed as cud, and also liquid food directly. It acts as a strainer at the entrance of the fourth stomach, to prevent the passage of coarse particles. Psaltery. A dulcimer, played with the fingers or a plec

trum instead of by hammers. The psaltery was the prototype of the spinet and harpsichord. Notwithstanding the general use of keyed instruments in 1650, it was considered second to none when played with a skilled hand. Psammetichus I. King of Egypt 666-612 B.C.; able ruler and extensive builder.

Psammitic. In Geology, having a structure like sandstone, made up of rounded grains of sand. If the grains are sharp, the structure is called gritty.

Pseudamnion. Membrane secreted inward from the pseudo-chorion in Mustelus, and tense with amniotic fluid. Pseudarachna. Division of Arachnida, including Pantopoda and Tardigrada. Pseudembryo. Larva of an Echinoderm, in which by a new and peculiar developmental process the young of the adult is formed. The process is analogous to the metamorphosis of certain insects.

Psaltery.

Pseudepigrapha. Uncanonical writings, falsely attrib-
uted to prophets and apostles; akin to the APOCRYPHA (q.v.)
of O. T. and N. T., but arbitrarily distinguished from them, less
familiarly known, and usually inferior. The Teaching of the
Apostles, pub. 1883, has historical value.

Pseudhæmal, or PSEUDOHÆMAL.
lids, Echinoderms, etc.
Blood system of Anne-
It in some cases communicates with
the body cavity, and even the external water can in some in-
stances be directly mixed with this false blood. It contains a
few corpuscles.

Pseudoadiabatic. Atmospheric changes in which the
quantity of contained heat is unchanged, but its effect is
changed by reason of the precipitation of condensed vapor.
Pseudobranch. Remnant of a gill in the spiracle, on
the mandibular arch of sharks; also a similar remnant on the
operculum or hyoid arch in Teleosts.

Pseudobulb. Enlarged basal parts of epiphytic orchids and some other plants.

Pseudo Butyl Alcohol. CH.CH2.CHOH.CH,. Secondary butyl alcohol; liquid boiling at 87° C. See BUTYL ALCOHOL. Pseudochorion. Membrane derived from the foetal compartments of the oviduct of Mustelus.

Pseudocol. See ARCHICŒL.

Pseudocumene. C,H,(CH,),. Bpt. 170° C. Trimethylbenzene. Liquid hydrocarbon, constituent of coal tar, from which it is prepared indirectly.

Pseudocysts. Masses of protoplasm, containing chlorophyll, a number of which compose the minute individual organisms of the classes Protococcoidog

Pseudodipteral. In Classic Architecture, denoti outer colonnade to the wall of the cella retained. the inner row of columns is omitted and the space fr

Pseudofilariæ. Little nematode-like vermiform produced in pairs at the end of certain Gregarines for pu of reproduction.

Pseudogaster. Secondary cavity, occurring in s by growth, folding, coalescence, or even fusion of differ dividuals: into it excurrent or even paragastric canals o Pseudogastrula. Stage in the development of ca ous sponges, in which the granular cells of the amphibl are temporarily invaginated within the flagellated cells. stage occurs while the embryo is receiving nutriment fro maternal tissues; when the larva is set free, the inner cel evaginated so as to restore the amphiblastula which pre true gastrulation. Pseudoisidorian Decretals. decrees of the earlier Church, immensely enhancing epis Collection of spu and papal authority. It appeared probably ab.850. Pseudomorphs. Minerals which deviate from the of crystallization peculiar to that species, either by alter or substitution.

Pseudonavicellæ. Little spindle-shaped, incased s resulting from the division of encysted and conjugated Gi rines.

Pseudoneuroptera. Group of Orthoptera, inclu three tribes, Physopoda, Corrodentia, and Amphibiotica. Pseudonym, NOM DE PLUME, or PEN-NAME. Assumed familiarly known than the real name, as in the cases of Ge an author; often retained through life, and sometimes n Sand, George Eliot, Jean Paul, Pierre Loti, Ouida, Mark Tw Artemus Ward, E. Marlitt, Lewis Carroll.

Pseudoparenchyma. Mycological term for fung tissues composed entirely of matted or interlacing hyphæ. Pseudopodia. from the body of a Protozoan or from the swarm spores of The projecting masses of protopla Myxomycetes; also certain stalks supporting the capsule in Bog-mosses, and certain stalked gemmæ in the genus A comnion and other mosses.-In Zoology, protrusions which be produced from the wall or the substance of amoeboid c and retracted at pleasure: the substance of the protrusion ag podia are the locomotor organs of the amoeba, hence the na becoming a part of the general protoplasm. Lobose pseu False-feet.

Pseudoprocts. See OSCULUM and PSEUDOSCULA. Pseudopupa. Stage which intervenes between the lary stage and the pupa in bees and wasps.

the genera characterized by elongated forms, but an absen Pseudoraphideæ. Order of Diatomacea, comprisin of the raphe or median line connecting the nodules.

Pseudoscope. Variety of stereoscope, through which, one look at a solid object, the concave parts appear conve and the convex parts, concave.

Pseudoscorpionidæ, or CHELIFERIDA.
nids, resembling Scorpions, but
without caudal spine and poison
gland; the hinder part of the ab-
domen does not form a narrow,
special post-abdomen. They have
two or four eyes, two pairs of stig-
mata, and spinning glands. The
book-scorpion is an example.

Secondary pores produced in
Pseudoscula (PSEUDOSTOMES).

Small Arach

Sponges by proliferation and fold- Book Scorpion (Chelifer can-
ings of the cortical portions. There
croides).

are two sorts: (1) vestibular, those leading to incurrent canals;
cloacal, those leading from excurrent canals; these should be
to these the word pseudostomes should be restricted; and (2)
called pseudoprocts.

Pseudotetramera. See TETRAMERA.
Pseudotrimera. See TRIMERA.

Pseudovaries. Ovaries as in Aphides. They produce ova capable of development without fertilization. See PARTHENO

GENESIS.

Psilomelane. Important ore of manganese, frequently associated with pyrolusite. It is often impure or of less definite chemical composition than the other ores from which manganese is obtained. See MANGANESE ORES.

Psilo

1236

PSITTICIDE-PSYCOPHYSICS

Psittacidæ, or PSITTACI (PSITTACOMORPHA; PARROTS). Group of Scansorial Birds, living in warm climates, especially of America. The beak is stout, the upper mandible is movably joined to the frontal bone, and curved over the short and broad lower beak. The tongue is fleshy, the legs short, strong, and with very short metatarsus. The four toes are

Arara Cockatoo (Microglossus aterrimus).
arranged in pairs, so as to be opposable, and can be used like a
hand to grasp with. The plumage is usually green. Here be-
long the PARROTS, MACAWS, and COCKATOOs (q.v.). The last are
Australian, and bear an erectile crest of feathers on the head.
Most of the Parrots are African; a few are neotropical. The
Macaws are wholly neotropical, and are distinguished by their
long tails.

Psittacomorphæ. Order of Birds, including the Parrots.
See SCANSORES.

Psoriasis. Disease of the skin, chronic in form, and apt
to recur, with an eruption, at first of circular patches, after-
ward spreading and assuming different shapes. These patches
are dry and inflamed, and covered with a crust of mother-of-
pearl-like scales, a distinction from PITYRIASIS (q.v.). It very
frequently attacks the scalp. Arsenic has probably been relied
upon more than any other remedy in the treatment of this
disease.

Psorosperms. Little spore-like Gregarines, living para-
sitically in the tissues of Mammals, gills of Fishes, etc. Their
full life history is not known.

Psyche. Personification of the soul, loved by Cupid,
abused by Venus; finally made immortal and united to Cupid;
in art represented as a maiden with the wings of a butterfly.
Psychic Theory of Heredity. This refers the phe-
nomena of development, transmission, sex, phylogenetic vari-
ation, etc., to the powers of mind. Protoplasm is conceived
to be living and different from other matter; first, because it is
a mechanism rather than a substance, and, secondly, is under
the control of spirit forces. Hence it is educable and capable
of developing into brain tissue, and exhibiting powers of
memory, sensibility, volition, and other powers distinguished
strictly as psychic. See ARCHÆSTHETISM, PANAESTHETISM, and
LAMARCKIANISM.

Psychology. Science of mind. Leaving out of account
the nature of mind, which becomes a problem of metaphysics,
it concerns itself solely with mental processes. The contents
of the mind, as sensations, thoughts, feelings, impulses, judg-
nts and their processes, make up its subject matter. But
of inner experience, and just here lies
for the science, for

It

one's own observation of one's own states of consciousness
introspection, an act notoriously difficult; and to make
difficulty still greater, these states are altered by the very
of observation. It has been the aim of modern psycholog
obviate this difficulty, so far as may be, by obtaining condi
and relations to which methods of greater exactness migh
applied. From the beginning of philosophic thought an
the Greeks, psychology was inextricably interwoven
metaphysics and epistemology, and it is only within com
tively recent times that it has attained an independent fo
as a subject of investigation. This separation from ge
philosophy and the application of scientific methods have
the chief characteristics of modern psychological prog
Regarded as a science, it is still in the early stages.
lowers are busy with analysis and accurate description
attempts at synthesis, more or less successful as they ma
are never final. Having achieved independence, psych
has proceeded to subdivide itself. A glance at these su
nate fields will give perhaps the clearest idea of the sco
the general subject. If we may disregard introspective
chology, the foremost of these minor divisions, at least fro
number and zeal of its workers, is Experimental Psych
This is an attempt to apply purely scientific methods to n
phenomena, and the underlying idea is usually Measure
This quantitative estimate is arrived at by experimental
ment of the body and observation of consequent chan
consciousness, the assumption being made that every
change has its accompanying nervous change. By obt
thus a quantitative expression of the nervous series, it is a
that it may be possible in the light of this to determine
lations of the corresponding mental series. Numerous
ratories for the prosecution of such experiments hav
founded in different countries, notably in Germany a
U. S., and many experimental psychologists are at work
PSYCHOMETRY, PSYCHO-PHYSICS, and FECHNER'S LAW.)
ological Psychology is the study of the physiology of th
ous system in so far as it bears upon the facts of conscio
The relation between mind and brain is the highest exp
of its subject matter, and as usually conceived it includ
topics as hypnotism, etc., the nature of which is n
enough understood to allow their reference to any
division of psychology. Abnormal Psychology deals w
normal states of mind in their relation to the normal, an
light has been thrown upon mental processes by the s
insanity, idiocy, hysteria, and the various mental affec
pathological nervous states. Comparative Psychology
two great divisions; first, the comparative study of ma
ferent levels of civilization and development, sometim
Folk Psychology and depending upon the results of an
ogy and ethnology for its material; second, the manife
of consciousness of the lower animals, a side of the
of particular value and suggestiveness. Child Psych
an extension of this comparative and genetic study t
where we can inspect the human mind in its simplest
sions. Practical applications of the knowledge won by
modern activity are already being seen in various fie
ment of the insane and the defective and delinquen
ably in education, as a result of child study, and in t
generally.

Psychometry. Science which deals with the
ment of the duration of mental acts; often spoken o
chology as the measurement of reaction times. E
observer be required at a given signal, say of sound,
telegraphic key, and the moment at which the signal
be recorded, as well as the moment at which the key i
the difference between the two records will represent t
reaction time of the observer for an auditory stimul
time does not represent a purely mental process. It
up of the time taken for the stimulus to pass from the
ear to the brain center, the time of perception, and
will leading to the proper motor response, and th
motor impulses being approximately known, by su
transmission of the motor impulse from the brain
those two elements from the whole reaction time
sponding finger. The rate of transmission of ser
the duration of the purely mental processes of
difficult. The same principles are applied to the mea
and volition. The separation of these two element
of association times. See PERSONAL EQUATION and
EQUATION MACHINE.

Psychophysics. That side of experimental p
which deals with the measurement of the intensity
tion. The problem is to obtain a formula of the rela
the resulting sensation, for the different senses. S
mula, which within certain limits holds good for m
incr
ing between the intensity of the external stimulus a
senses, has been found in Weber's Law, which is, ro
in order that the intensities of sensations may
rithmetical series, the stimuli must increase in a g

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es of consciousness, or ult; and to make the Itered by the very fart modern psychology ta by obtaining conditions er exactness might be sophic thought among bly interwoven wi s only within compare an independent focu paration from gener tific methods have been Osychological progress early stages. Its fal curate description, and cessful as they may se dependence, psychology lance at these subor est idea of the scope if gard introspective per visions, at least from the perimental Psychology ntific methods to menti is usually Measurement. t by experimental treat E consequent changes made that every mea s change. By obtain ervous series, it is arge this to determine thes series. Numerous la n experiments have be ly in Germany and to ologists are at work. FECHNER'S LAW.) Pay he physiology of the e the facts of consciousnes is the highest express conceived it includes ure of which is not re reference to any dis Psychology deals with on to the normal, and m processes by the stair various mental affections rative Psychology indu arative study of masin elopment, sometimes a d on the results of anthro second, the manifestati mals, a side of the se -ness. Child Psycholog nd genetic study to 17 nind in its simplest ex e knowledge won bral seen in various fields.r ild study, and in the tr tive and delinquent clase eh deals with the meas acts; often spoken of is p reaction times. Eg, f nal, say of sound, to pr at which the signal is t at which the key is pe ords will represent the st - an auditory stimulas. D mental process. Its ulus to pass from the ex of perception, and the a or response, and the time Ise from the brain to the transmission of sensory ately known, by subtra -hole reaction time we ental processes of per

f these two elements B

re applied to the meas ONAL EQUATION and PIST

e of experimental psyc

ment of the intensity of s

a formula of the relation e external stimulus and

e different senses. Such

its holds good for most r's Law, which is, rough sensations may increase must increase in a ge

PSYCHROMETER-PUBLIC DEBTS

series. The true interpretation of Weber's Law, or its mathe-
matical expansion, known as FECHNER'S LAW (q.v.), is a matter
of dispute. There are practically three theories in the field:
(1) that held by Fechner himself, that it is a formula of ulti-
mate relation between mind and body; (2) that it is purely
psychological in character; and (3) that it is purely physio-
logical. The two latter theories have adherents; Fechner's
interpretation is now practically abandoned.

Psychrometer. Instrument for determining the amount
of moisture in the air. It is sometimes called the wet and dry
bulb hygrometer, and was devised by Mason, although on the
Continent it is known as AUGUST'S PSYCHROMETER (q.v.).

Ptah. Probably the oldest of the Egyptian deities. The father of the gods. He was regarded as the creator of the world.

Ptenoglossa.

Division of Ctenobranchiata, including forms having the lip of aperture of the shell entire, siphons absent, and the radula armed with transverse rows of numerous small hooks, but with no median teeth. Janthina and Solarium are examples.

Pteranodon. Genus of flying Saurians, with jaws toothless and tail short and slender; comprising gigantic forms from the Cretaceous of N. America.

Pteraspis. Primitive type of small Cephalaspidian Upper Silurian fishes(?), having a bony snout, and the head and the fore part of the body covered with bony plates.

Pterichthys. Placoganoid with arm-like fins; first discovered by Hugh Miller in the Old Red Sandstone of Scotland. See PLACODERMS.

Pteridium. See SAMARA.

Pteridology. Study of Ferns.

Pteridophyta. Sub-kingdom of plants, also known as
Acrogens and Vascular Cryptogams. It includes the ferns and
their allies, lycopods or club-mosses, Equiseto or horsetails,
Rhizocarpea and Selaginellaceae, having their greatest develop-
ment in tropical regions, and a very great antiquity dating
from the Silurian. They were the first land plants.

Pterobranchia. See POLYZOA and ASPIDOPHORA.
Pterocardiac Ossicle. See GASTRIC MILL.

Pterodactyls. Flying reptiles of the Mesozoic period.
They resembled bats, but had only 4 fingers, the outermost
alone being elongated to hold the web. They had 4 toes. The

Pterodactylus crassirostris.

head was birdlike with a beak, usually toothed. Some were
fish eaters, and some large, the allied Pteranodon of the Amer-
ican Cretaceous having a spread of wing of 20 ft. They belong
to the order Pterosauria (Ornithosauria).

Pteromys. See SCIUROMORPHA.

Pteropoda. Class of Mollusca, including forms not having a sharply defined head, but with two wings or fin-like expansions (epipodia), on the rudimentary foot. The mouth is surrounded by tentacles, or by two tentacles bearing suckers (cephalic cones). Sometimes a shell is present. They are hermaphrodite and pelagic (free swimming). Two orders are included, Thecosomata and Gymnosomata.

Pteropodidaæ. See BATS.

Pterotic. Posterior and most external of the projecting bones in the cranium of a fish. It is an element in the ear capsule.

Pterotracheidæ. Family including slug-like pelagic Mollusks: without a shell, and with a well developed mesopodium, bearing a sucker in the males. See HETEROPODA. Pterygotus. Gigantic Crustacean, very similar to Eurypterus, but with the eyes marginal and bilobate tail; called by

the Scotch quarrymen Seraphim, from the wing-like f feather-like ornament of the thoracic appendage.

Pterylæ. Areas on a bird's body that bear feather are separated by apteria or naked spaces. See PTERYL ing on PTERYLOSIS (q.v.). Pterylography. Science, originated by Nitzsch

Pterylosis. Distribution of the ptilosis or pluma bird in PTERYLE (q.v.). In Penguins and struthiou there are no apterial spaces, but in more highly de birds there are definite pterylæ, with considerable Apteria are generally present along the middle of the and especially along the belly.

Ptolemaic System OF THE UNIVERSE. The eart supposed to be the central body, the sun, moon, and stars revolving about it once per day. Special devices were imagined for representing the motions of the planets and inoon, so that predicted with such their places could be accuracy as was demanded at that time.

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Ptolemy. Thirteen kings of Egypt of this name, who reigned from 323 to 30 B.C. The founder of the dynasty was Soter, who had been a general of Alexander the Great, and became gov. of Egypt at his death. In 306 he assumed royal power, and in 301, after the battle of Ipsus, added Syria and Cyprus to his domin- Ptolemaic System of the Universe. ion.-II. PHILADELPHUS, 284-246, built canals, roads, and lighthouse on Pharos, and fostered schools and literatur III. EUERGETES, 246-221, restored the gods Cambyses had ried off, made conquests in Arabia and toward India, favored scholars at home. The line became extinct in C patra VII.

Ptolemy (CLAUDIUS PTOLEMÆUS). 2d cent. mathematician, astronomer, and geographer. His great w Egypt on astronomy, commonly known as the Almagest, and treatise on geography were the great authorities on th subjects for 1,400 years.

Ptolemy's Law. If a ray of light or other form of wa motion pass from a point A to a point B in the same mediu but reflected in its course by a plane surface, there is no pa from A to B by way of any point of the surface so short that actually traversed by the ray under the law of reflectio viz., that the angle of reflection equals the angle of inciden

Ptomains. Substances produced in the process of deco position of nitrogenous bodies; sometimes called putrefacti alkaloids. They are more or less directly the product of t action of bacteria, each ptomain being generated by its sp cific bacterium. Many of them are quite poisonous and gi rise to the sickness occasioned by eating meats, cheese, i cream, etc., after the putrefactive changes have begun.

Ptosis. Drooping of the upper eyelid, usually due to paralysis of the muscle that lifts the lid.

Ptychodont Dentition. Mammalian molar teeth wit the sides folded longitudinally, the folds often crossing th crown, as in the Rabbit.

Ptyxis. Folding or coiling of leaves in the bud. Puberty. Time at which the procreative power develops in European girls ab. 12 to 14, in boys later; somewhat earlie in the tropics; attended with dangers to health, especially with girls.

Puberulent. Diminutive of pubescent.

Pubescent. In Botany, organs covered with soft, simple

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hairs.

Publicans. Roman knights who farmed the public taxes: in the Gospels, their subordinates, odious to their Jewish tyrants. countrymen alike as extortioners and as agents of foreign

Public Debts. See APPENDIX.

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