and by cotton wool, anticipating the later observations of Pasteur,' Tyndall, Chauveau, and others to the same or similar effect. These results of experiments are commonly understood to prove the particulate character of the agents so studied. What may be called an era in the practical application of etiological inquiry dates from the introduction by Lister (about 1860) of the principles of antiseptic surgery, based upon the theory that disease-germs, derived from the atmosphere or other external sources, are the essential causes of suppuration, septicemia, pyæmia, gangrene, etc. following injuries or operations.

So far from this inquiry being yet terminated, while experiments and observations have become more and more numerous and elaborate, opinions continue to differ; and we must yet await the time when, by successively excluding, one after another, all the sources of error, a truly scientific conclusion may be obtained.

Roughly speaking, it may be said that parties in the debate are chiefly ranged upon two sides-those who favor the probability that only chemical, not vital, action is to be traced in fermentation, putrefaction, suppuration, infection, and contagion; and those who regard minute organisms, discovered or undiscovered, as causative of, and indispensable to, all these processes.

2

Without intention of injustice to other able investigators, the principal names so far associated with the former of these views may be thus mentioned Panum (1856), Robin, Bergmann, Liebig, Colin, Lebert, Vulpian, Onimus, B. W. Richardson, Beale, Senator, Rosenberger, Hiller, Nægeli, Schottelius, Harley, Jacobi, Curtis, and Satterthwaite. Of those maintaining, in some form and with more or less positiveness, the disease-germ theory, the most conspicuous, especially as observers, have been Tuchs (1848), Royer (1850), Davaine, Branell, Pollender, Pasteur, Tyndall, Lister, Mayrhofer, Ortel, Letzerich, Nassiloff, Hueter, Toussaint, Hansen, Salisbury, Klob, Hallier, Basch, Virchow, Neisser, Eberth, Tommasi Crudelli, Klebs, Talamon, Schüller, Tappeiner, Cohnheim, Koch, Baumgarten, Buchner, Aufrecht, Birch-Hirschfeld, Greenfield, and Ogston. Besides these the elaborate studies of microphytes by Cohn, and those of Coze and Feltz, Waldeyer, Recklinghausen, and others upon septic poisoning, have been of acknowledged importance; and the experimental labors of Burdon Sanderson in England, and Sternberg, H. C. Wood, and Formad in the United States (under the auspices of the National Board of Health), possess great value. But the scientific caution of these last inquirers, like that of Magnin, has prevented them from formulating, as yet, positive and final opinions upon the subject. It is not saying too much to assert nearly the same of

1 Pasteur's experiments with long-drawn bent tubes had especial significance.

2 Dr. Richardson has long contended for the doctrine first proposed by Panum, that a peculiar chemical agent, (called by Bergmann sepsin) is the cause of blood-poisoning from virulent absorption or inoculation. Latterly, attention has been called by Selmi and other observers to the existence of complex compounds called ptomaïnes in decomposing animal substances-e. g. the human body after death-these having considerable resemblance in their toxic action to the poisonous vegetable alkaloids.

* Opposed at least to the ordinary form of the germ theory of disease.

Sternberg's observations and experiments (following those of Pasteur) with the inocu lation of animals with saliva, proving that even when taken from perfectly healthy men this may be fatally poisonous to animals, possess remarkable interest. They do no seem, however, to be decisive either way in regard to the germ theory of infection.

several of those mentioned above, as inclining to one or the other side of the controversy.'

It would appear, then, that the data for a final conclusion have not yet been made certain. Several hypotheses are conceivable, and capable, each, of plausible support :

1. The purely chemical theory of Liebig, Gerhardt, Bergmann, Snow of London, and B. W. Richardson.

2. The bioplastic hypothesis of Beale, according to which germinal matter may be detached from a living body and planted, while yet retaining vitality, upon another, and there may undergo changes more or less morbid, and destructive of the body by which it has been received. This theory of migrating or transplanted bioplasts has received very little support besides that of its distinguished author.

3. That the minute organisms discovered so constantly upon diseased parts of plants and animals (e. g. ergot of rye, Peronospora infestans of potato-rot, Botrytis Bassiana of silk-worm muscardine, Panhistophyton of silk-worm pebrine, Empusa musca of the fly, Achorion, Tricophyton, Oidium, and Leptothrix of human affections of the skin and mucous membranes) are incidental or accidental only2-acting, as R. Owen observes, 1 Billroth and Cohnheim are among those who have changed their opinions on this subject after prolonged investigation.

2 This possibility has not been as yet altogether ruled out in regard to Koch's Bacillus tuberculosis; concerning which active discussion has been going on during the past year or two (1882-83). A very large number of observers confirm the statement that the bacilli are found in most specimens of tubercle. Several, also, have repeated with success Koch's inoculation experiments, in which tubercle appeared to be propagated by carefully isolated bacilli. But many facts still stand in the way of the conclusion that the bacillus is the causa sine quâ non of tuberculosis. First, examples of the production of phthisis by apparent contagion or infection are few. Although Dr. C. T. Williams found bacilli in the air of the wards of the Hospital for Consumptives at Brompton, yet of the experience of that hospital Dr. Vincent Edwards, for seventeen years its resident medical officer, reports as follows: "Of fifty-nine resident medical assistants who lived in the hospital an average of six months each, only two are dead, and these not from phthisis. Three of the living are said to have phthisis. The chaplain and the matron had each lived there for over sixteen years. Very many nurses had been in residence for periods varying from months to several years. The head-nurses, says the writer, sleep each in a room containing fifty patients. Two head-nurses only are known to have died-one from apoplexy; the other head-nurse was here seven months, was unhappily married, and some time afterward died of phthisis. Of the nurses now in residence, one has been here twenty-four years, two twelve years, one eight years, one seven years, one six and a half years, and one five years. No under-nurse, as far as I am aware, has died of phthisis. All the physicians who have attended the in-and-out patients during the past seventeen years are living, except two, who did not die from phthisis."

Against the inoculation and inhalation experiments of Villemin, Tappeiner, Koch, Wilson Fox, and others, by which the specific character of tubercle has been said to be proved, must be placed those of Sanderson, Foulis, Papillon, Lebert, Waldenburg, Schottelius, Wood and Formad, Robinson, and others, by which tubercles have been induced by the injection, inoculation, or inhalation of various non-tubercular materials. In answer to the argument from these, it is asserted by Koch and his supporters that "there is no anatomical or morphological characteristic of tubercle," its only sufficient test being its inoculability. This is almost begging the question; at all events, it leaves it, for the present, unsettled. Moreover, tubercular deposits do not always contain bacilli, as has been shown by Spina, Sternberg, Formad, Prudden (N. Y. Medical Record, April 14 and June 16, 1883). The last named made, in one well marked case, six hundred and ninetyfive sections from ninety-nine tubercles in different portions of a tuberculous pleura, all of Koch's precautions being observed in the examination. Belfield (Lectures on MicroOrganisms and Disease) admits the possibility that tuberculosis may be produced by either of several causes. It has, at least, not yet been demonstrated that the tubercular tissue is more than a nidus or favorable "culture-ground" for the bacilli, or that, in the presence of a constitutional predisposition, they may not merely promote a more rapid destruction of the invaded organs or tissues.

most commonly as natural scavengers in the consumption of effete organic material; but that they may become noxious under two sorts of circumstances-viz. when their numbers are enormously increased, as is known to be the case with trichinæ in the human body, and also when they are brought in considerable number into contact with bodies already diseased, or at least suffering under depression of vital energy.

4. That such organisms are the essential and direct causes of enthetic maladies by invading the human and other living bodies as parasites, consuming and disorganizing their tissues, blood corpuscles,' etc. Pasteur considers the abstraction of oxygen an important part of their action.

5. That these microbes, microphytes, or mycrozymes act not as parasites, but as poison-producers, secreting a sort of ferment which is the specific morbid material (Virchow); or, when multiplying in excess of their foodmaterial, they may die, and their dead bodies, like other decaying organic matter, may become poisonous. This possibility, although not distinctly suggested (so far as I know) hitherto, appears to me to be not unworthy of consideration. That the numbers of micro-organisms present have some important relation to morbid conditions has long since been inferred from familiar facts.

6. That they are not generators, but carriers, of disease-producing poisons; their vitality giving to the latter a continuance of existence and capacity of accumulation and transportation not otherwise possible.

Briefly, the following is a summary of the most generally accepted classification of those microscopic organisms2 whose rôle in the causation of diseases is now under discussion; chiefly following Cohn and Klebs : Orders: Hyphomyceta, Algæ, Schizomycetæ.

Hyphomycetæ, genera: Achorion, Tricophyton, Oidium.
Algae, genera: Sarcina, Leptothrix.

Schizomycetæ, or Bacteria, genera: Micrococcus, Rod-bacterium, Bacillus, Spirillum.3

4

Micrococci (Sphærobacteria of Cohn) are asserted (under certain conditions) by Letzerich, Wood, and Formad to be causative of diphtheria; Ogston has found them in ordinary pus; Rindfleisch, Recklinghausen, Waldeyer, Birch-Hirschfeld, and others report them to be always present in the abscesses of pyæmia; Buhl, Waldeyer, and Wagner state their occurrence in intestinal mycosis; Eberth, Köster, Maier, Burkhardt, and Osler, in ulcerative endocarditis; Orth, Lukomsky, Fehleisen, and Loeffler, in erysipelas; Coats and Stephen in pyelo-nephritis; Friedländer, in pneumonia; Eklund (Plax scindens) in scarlet fever; Keating and

Against this view stands especially the objection that, as Cohn, Burdon Sanderson, and others have fully shown, bacteria and other Schizomycete obtain their nitrogen, not from organized tissues, but from ammonia, and their carbon and hydrogen from the results of decomposition in organic tissues. (See B. Sanderson, in Brit. Med. Journal, Jan. 16, 1875.) Pasteur has regarded the relation of these organisms to oxygen as important; some of them requiring it for their existence (ærobic), and others not (anærobic). He has defined fermentation as "life without free oxygen."

For further details concerning these the reader is referred to the works of Magnin, Belfield, and Gradle on The Bacteria, and on the Germ Theory of Disease.

Cohn also separates vibrio and spirochete as genera distinct from spirillum. They may, however, be regarded rather as species of that genus. Some recent authors included bacterium and bacillus under one genus, bacillus; against which simplification there seems to be no valid objection.

Bulletin of National Board of Health, Supplement No. 17, Jan. 21, 1882.

The Medical News, Philadelphia, July 29, 1882.

Le Bel, in measles; Leyden and Gaudier, in cerebro-spinal meningitis ; Carmona del Valle, in yellow fever; Prior, in dysentery; Gaffky, Leistikow, Bokai, and Bockhardt, in gonorrhoea; besides other similar observations by numerous writers.

Bacterium termo is regarded by leading authorities as the special ferment or causative agent of putrefaction 2 (Billroth, Cohn).

Bacillus includes, hypothetically at least, several species; as Bacillus subtilis, the innocent hay-fungus; Bacillus anthracis, the microbe of malignant pustule (anthrax, milzbrand, charbon) and the splenic fever of sheep; Bacillus typhosus (Klebs, Eberth, Meyer) of typhoid fever; Bacillus lepræ (Hansen, Neisser, Cornil, Koebner) of leprosy; Bacillus malariæ, reported as having been demonstrated by Klebs and Tommasi

Crudeli, Marchand, Ceri, and Ziehl; Bacillus tuberculosis (Koch, Baumgarten, 1882); the bacillus of malignant cedema (Gaffky, Brieger, Ehrlich); that of syphilis (Aufrecht, Birch-Hirschfeld,5 Morrison); of glanders (Loeffler, Schuetz, Israel, Bouchard); of pertussis (Burger); besides the Actinomycosis of Israel, Ponfick, Bollinger, and others. Koch has very recently (1883) been reported to have discovered in Egypt the bacillus

6

of cholera.

Spirillum (Spirochata of Ehrenberg) has its best ascertained example in the minute forms first observed by Obermeier, and afterward by many other observers, in the blood of patients suffering with relapsing

FIG. 2.

Bacteria: a, zoogla of Bacterium termo; b, pellicle of bacteria form of B. lineola,

fever. They have been found present in the blood only during the febrile paroxysm, disappearing in the intermission and through convalescence.

Hastening to close our consideration of this subject, we may note, without much argument, a few of the points of difficulty

from surface of beer; c, Bacterium lineola, free; d, zoogia needing yet to be more fully illuminated by care

1 Sternberg's careful experimentation seems to show the identity of Neisser's gonococcus with the Micrococcus ureæ, commonly found in decomposing urine.

2 Others have referred putrefaction to vibriones, less precisely described.

3 Dr. H. D. Schmidt of New Orleans, an experienced pathologist, reported (Chicago Medical Journal and Examiner, April, 1882) that critical examination of numerous specimens of tissues from three cases of leprosy under his care failed to verify the existence of bacilli as characteristic of that disease.

Not certainly, however, as shown by Sternberg (Bulletin of Nat. Board of Health, Supplement No. 14, July 23, 1881). Dr. Salisbury of Ohio in 1866 made a series of observations, on the basis of which he asserted the discovery of a genus of malarial microphytes, which he referred to the family of Palmella.

The oval and spherical organisms described by Richard and Laveran as found in the blood of malarial patients resembled micrococci rather than bacilli. 6 Die Actinomykose, 1881.

5 More recently described by him as micrococci.

ful observation before any form of the germ theory can take its place as an established doctrine in etiology:

1

1. The absence of the characters belonging to definite organisms in the easily-studied virus of small-pox and vaccinia stands, a priori, against

the probability of such organisms being essential to the causation of other enthetic diseases.

2. Analogy in nature, showing the commonly beneficial action of nutritive processes in re-appropriating the products of organic decay on a large or on a small scale, makes the scavenger theory of the general function of minute cryptogamic organisms more probable, per se, than that which holds many of them to be destructive parasites or poison-producers in the bodies which they may inhabit. Few well known parasites are capable of causing death in higher animals or in man.

3. These microbes are among the minutest objects which can be studied under the microscope. Bacteria average about 6 of an inch in their longest diameter; micrococci and spores (Dauersporen, Billroth) are yet smaller. Much care, therefore, as well as skill, must be exercised in making observations upon them.2 Huxley asserted a few

The particulate character of variolous and vaccine virus has been already alluded to, as asserted to have been shown by Chauveau and others. Yet it is not absolutely demonstrated that filtration may not produce an important chemical alteration in some kinds of highly unstable organic material subjected to it. Cohn figures a Micrococcus vaccinia in his article on Bacteria (Microscopical Journal, vol. xiii., N. S., pl. v., Fig. 2). Beale denies (Microscope in Medicine, 4th ed.) the existence of any organisms in vaccine virus. Lugginbuhl, Weigert, Klebs, Pohl-Pincus, and others have asserted their existence, but, especially in the absence of any successful culture experiments, it does not seem to be proved.

A very interesting discovery was made by Tyndall, to the effect that while one boiling of a liquid would sterilize it for the time by destroying all the bacteria present, their spores might still retain vitality and be afterward developed. By repeated exposure to a boiling temperature, taking these spores in their developing stage, they were destroyed, and complete sterilization was effected.