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Molecules. The smallest physical particles of matter that can exist in a

separate state. They are probably always constituted of two or more

atoms. Morphology. The science which treats of the forms and structures of living

beings. Morula. The stage of development of the ovum after segmentation, in which

all the young cells are alike, before the blastoderm is formed. Mucin. The characteristic constituent of mucus. Müllerian duct. An embryonic structure from which are formed the genital

passages in the female, viz., Fallopian tube, uterus and vagina. Mydriasis. A dilated state of the pupil. Myograph. An instrument for graphically recording muscle contraction. Myopia. The condition in which the focus of parallel rays of light falls short

of the retina ; short sight. Myosin. The substance formed by the coagulation of muscle plasma. It is

one of the globulins. Natural nerve currents. The electrical currents passing through an exposed

muscle or nerve while in a state of rest. Neuroglia. The reticular connective tissue which binds together the elements

of the nerve centres. Non-polarizable electrodes. Electric terminals specially constructed so as

not to set up secondary currents on application to moist living tissues. Notochord. The primitive vertebral axis of the embryo. Nucleolus. A small spot observable in some nuclei. Nucleus. A central part of a cell differentiated from the main protoplasm,

commonly round, but sometimes elongated, as in muscle.

Odontoblasts. Living cells lining the pulp cavity of the interior of a tooth,

and presiding over the growth and nutrition of the dentine. Olfactory. Pertaining to the sense of smell. Omphalo-mesenteric. The vessels connecting the embryonic circulation

with the yolk sac, which are early obliterated in the mammalian fætus. Ophthalmoscope. An instrument consisting of a small mirror, by which

the interior of the eye can be illuminated so that the fundus may be viewed. Optic cup. The involuted optic vesicle which is developed into the retina, etc. Osteoblast. The active cells in forming bone. Osteoliths. Calcareous particles lying in the endolymph. Oxyhæmoglobin. The coloring matter of the blood corpuscles. Paraglobulin. One of the more abundant albumins of the blood-serum

globulia. Paramecium. A unicellular organism composed of a soft mass of protoplasm

enclosed in a firmer case, and covered with motile cilia. Parapeptone. A body produced in gastric digestion during the formation of

peptone. Pepsin. A ferment existing in the gastric juice which converts proteids into

peptones. Peptone. A form of albumin which is produced during the digestion of pro

teids; it is very soluble, and diffuses readily through a membrane. Perilymph. The liquid surrounding the membranous labyrinth of the ear. Peristalsis. The mode of contracuion of the muscular walls of certain tubes

as the cesophagus and intestine, the effect of which is to cause a progres sive constriction, and so force the contents of the tube onward.

Phakoscope. An instrument for estimating the changes in the shape of the

lens during accommodation, by doubling the reflecteil images with a prism. Placenta. The intra uterine organ by means of which the fætal blood is

brought into close relationship to that of the mother, so as to gain nutri

ment and oxygen, and get rid of effete matters. Plasma. A term meaning anything formed or moulded; used in physiology

to indicate chemically complex kinds of matter which subserve to the forma

tion of the living tissues. Poikilothermic. Varying in temperature. A term applied to those animals

whose temperature varies with that of the surrounding medium-“cold

blooded animals." Presbyopia. A loss of power of accommodation for near vision which accom

panies old age. Prosencephalon. That part of the developing anterior cerebral vesicle srom

which are formed the olfactory and optic lobes, the hemispheres, and cor.

pora striata and optic thalami. Protista. A large group of organisms which remain in the primitive state of

a single cell during their lifetime. Protococcus. A unicellular vegetable organism, the proloplasm of which con

tains chlorophyll. Protoplasm. The substance which gives rise to the primitive vital phenomena,

seen in unicellular organisms, and which is the chief agent in executing the

functions of all the active tissues. Protovertebræ. The primitive segments of the mesoblast in the site of the

future vertebral column. Protozoa. That division of the protista which has been assigned to the animal

kingdom. Proximal. A term used to denote a part relatively nearer to the centre. Pseudopodia. Projections thrown out by moving protoplasm, by means of

which cells, such as amabæ, move. Ptosis. Drooping of the eyelid accompanying paralysis of the third nerve. Ptyalin. The ferment of the saliva. În a weak alkaline solution it converts

starch into dextrine and sugar.


Reflex action. The activity caused by a ganglion cell reflecting an afferent

impulse along an efferent nerve to the neighborhood of original stimulation. Reflexion. The return of rays of light from a surface. Refraction. The bending which rays of light undergo when passing obliquely

from one medium to another of different density, Reticulum. A network; a term applied to the interlacement of fibres, seen

in reticulated connective tissue, etc. Rheoscopic frog. An arrangement by which the change in the electric cur.

rent of one muscle of a frog is made to act as a stimulus to the nerve of another.

Saponification. The formation of soap; the decomposition of oils or fats by

means of alkalies into salts of the fatty acids and glycerine. Sarcolactic acid. The principal acid in dead muscle. It has a dextro-rota

tory power on polarized light, which ordinary lactic acid does not possess. Sarcolemma. The delicate sheath surrounding the fibres of skeletal muscles. Sclerotic. The fibrous coat of the eyeball. Sensorium. That part of the nerve centres supposed to receive sensory im


Somatopleure. The subdivision of the mesoblast which, with the attached

epiblast, forms the body walls of the embryo. Specific gravity. The relation of the weight of a given volume of any sub

stance to the weight of an equal volume of distilled water at 4° C. Spherical aberration. An indistinctness of the image caused by the differ.

ence in refraction at the centre and margin of a lens giving rise to different

focal lengths. Sphygmograph. An instrument for obtaining a graphic representation of the

pulse wave by means of a lever applied to the radial artery at the wrist. Splanchnopleure. The subdivision of the mesoblast which, with the attached

hypoblast, forms the chief visceral cavities of the embryo. Sporadic ganglia. Swellings occurring in the course of the peripheral nerves

caused by a group of nerve corpuscles. Steapsin. A ferment existing in the pancreatic juice which causes or aids the

saponification of the sats. Sudoriferous glands. The small tubular glands of the skin which secrete

perspiration. Summation. The fusion of several single contractions of muscle to form a

tetanic contraction; the accumulation of stimuli. Sutures. Unions formed by the direct apposition of bones without intervening

cartilage. They do not permit of motion. Sympathetic nerve. The ganglionic nervous cord on either side of the ver

tebral column. It transmits most of the vasomotor impulses coming from

the cerebro-spinal centres. Symphysis. A form of joint without synovial membrane in which the bones

are fixed together by fibro-cartilage. Synthesis. The artificial construction of a chemical compound from simpler

materials. Systole. The period of contraction of the heart's muscle.


Taurocholic acid. An acid existing in combination with soda in the bile. Tetanus. In physiology is used to denote the prolonged contraction of the

skeletal muscles which follows rapidly repeated stimulations or nervous

impulse. Thalamencephalon. That part of the anterior cerebral vesicle which is left

after the differentiation of the optic thalami, cerebral hemispheres, etc. Thrombosis. The occlusion of a vessel by a local coagulation of the blood. Trabeculæ. Supporting bars of tissue passing through some organs, such as

those proceeding from the capsule to the interior of the spleen or lymphatic

glands. Trophic. Relating to nutrition. Trypsin. A serment in the pancreatic juice which in alkaline solutions con

verts proteids into peptones. Tyrosin. A substance formed together with leucin during pancreatic diges

tion; it is also produced by putrefaction of proteids.

Urachus. The bond of union which at an early period connects the urinary

bladder with the allantois in the embryo; it is subsequently obliterated in the foetus.

Vacuoles. Small cavities occurring in cells. They are supposed to have im

portant functions in the unicellular organisms.

Vagus. The part of the eighth pair of nerves distributed to the viscera of the

throat, thorax and abdomen; the great regulating nerve of the vegetative

functions. Vaso-constrictor. Those impulses which excite contraction of the vascular

muscles. Vaso-dilator. Those impulses which inhibit the action of the vascular

muscles. Vasomotor. Those nervous mechanisms controlling the movements of the

blood vessels. Villus. A hair-like process. A term applied to the small projections charac.

teristic of the small intestine. They contain blood vessels and lacteals, and

are important in absorption. Vitellus. The yolk of the ovum, which in mammals divides completely to

sorm the embryo. In birds only a part divides, and the rest serves to

nourish the chick. Vorticella. Bell animalcule, a bell-shaped unicellular organism with a rudi

mentary, ciliated mouth cavity and rapidly contractile stalk. Wolffian body. An embryonic structure, the forerunner of certain parts of

the genito-urinary apparatus. Zymogen. A peculiar substance supposed to give rise to the pancreatic





BDOMINAL respiration, 332. | Amoeba, 39.
Abductor nerve of the eye, 523.

change in form, 83.
Abnormal constituents in the urine,

effect of stimulation, 83.

life of, 91.
Absorbents of stomach, 149.

locomotion of, 83.
Absorption, 190.

pseudopodia of, 83.
intestinal, 199.

Amceboid movement of white blood
interstitial, 192.

corpuscles, 226.
mechanism of, 203.

Amount of blood in the body, 215.
Accommodation, 570.

Amphioxus, blood of, 228.
Acid albumin, 69.

Ampull of semicircular canals, 608.
Acinous glands, 131.

Amylopsin, 167.
Active tissues, 43.

Analgesia, 623.
Adipose diarrhoea, 206.

Anelectrotonus, 508.
Afferent nerve, 48, 498.

Animal heat, 428.
Agminate glands, 202.

production of, 431.
Air passages of lung, 326.

Anode, 503.
Albumin, acid, 69.

Anterior roots of spinal cord, 617.
alkali, 70.

Anus, III.
coagulated, 70

Aortic arches, 716.
conversion into peptone,

valves, 263.
· 155.

Apnea, 347

Area opaca, 674.
in the urine, 406.

pellucida, 674.

Arterial blood, 355.
syntonin, 69.

pulse, the, 307.
tests for, 67.

system, development of, 716.
Albuminates, 69.

tone, 317
Albuminoids, composition of, 72. Arteries, small, 284.
Albuminous bodies, 66.

walls of, 283.
as food, 97, 100. Arterioles, 286.
Albumins, classification of, 68.

Arthrosis, 479.
chemical composition of,

Arytenoid cartilages, 487.

Asphyxia, 362.
characteristics of, 71. Assimilation, 31.
Alcoholic fermentation, 78, 90.

Astigmatism, 574.
Alimentary canal, 111.

Atmospheric air, 351.
development of, 697.

Atoms, 30.
Alkali albumin, 70.

Auditory nerve, stimulation of, 610.
Allantoin, 76.

terminals of, 607.
Allantois, 679.

Auerbach's plexus, 127.
Alveoli, 339.

Augmentation, 517.
Amnion, 675.

Auricles of the heart, 259.

egg, 68.

serum, 68.

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