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 only[19]--acting, as R. Owen observes, {141} 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. [Footnote 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