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 muscæ of the fly, Achorion, Tricophyton, Oidium, and Leptothrix of human affections of the skin and mucous membranes) are incidental or accidental only19—acting, as R. Owen observes, 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.
19 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 ninety-five 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 Micro-Organisms 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.
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,20 etc. Pasteur considers the abstraction of oxygen an important part of their action.
20 Against this view stands especially the objection that, as Cohn, Burdon Sanderson, and others have fully shown, bacteria and other Schizomycetæ 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."
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 food-material, 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 organisms21 whose rôle in the causation of diseases is now under discussion; chiefly following Cohn and Klebs:
Orders: Hyphomycetæ, Algæ, Schizomycetæ.