488 THIRD PART.—BACTERIA OR SCHIZOMYCETES. 
assumes in the course of generations various morphologically and physiologically 
unlike forms one after another, and these forms, in the course of yearsand decades of 
years, may produce souring in milk, butyric acid in sauerkraut, ropiness in wine, putre- 
faction in albumen and decomposition in urine, may turn articles of food containing 
starch red, and give rise to diphtheria, to typhus, to recurrent fever, to cholera, to 
intermittent fever’—these words or the view which they embody would not have been 
published even in 1877, if their author had studied the forms in question, and especially 
the parasitic forms, with greater attention. At the present day, when our knowledge 
of the facts is still more advanced, such a position can no longer be maintained. It 
is specially in the domain of the parasitic Bacteria that investigation has established 
more and more distinct species, and shown that every disease incited by a parasite 
which has been thoroughly examined may be traced to a definite form of Bacterium, 
of the specific character of which there can be as little doubt as of that of a large Fungus 
or of a worm. The assertion that there are distinct species of parasitic Bacteria, and 
that every special disease caused by Bacteria is the work of a distinct species, is not 
merely a convenient form of statement, as Nageli thinks, but it is the only one which 
is in unison with the /ac/s as at present known. 
If a species like the Bacillus of anthrax also vegetates as a saprophyte, it is 
obvious that it may set up different processes of decomposition in the dead substratum 
from those which constitute disease in a living body. Further, if diseases supposed to 
be due to the presence of Bacteria ‘have a limited duration in the history of the 
human race, change, arise and disappear,’ this is no objection to the observed facts 
but merely a reason for making special efforts to explain them ; and accepting the 
fact, equally well observed, that men as well as Bacteria may change some of their 
qualities in the course of time and yet retain their specific characters unaltered, we 
may suppose that the attempts at explanation will possibly in course of time be 
successful. 
It is uncertain whether there are obligate as well as facultative parasites among 
the Bacteria, either species that are strictly obligate or some that have also a 
narrowly limited power of saprophytic vegetation. The forms which may possibly 
excite diseases that are strictly contagious, smallpox for example, should be tested 
on this point. Mention must be made in this connection of Spirochaete Ober- 
meyeri, one of the most characteristic parasites and an undoubted inciter of disease, 
which appears invariably in the blood of those who are suffering from recurrent 
fever. It has been successfully transferred from men to apes, but to no other species 
of mammal on which the experiment has been tried. It has been attempted to 
cultivate it outside the body of a living animal, but as yet without success !. 
It is very doubtful whether the minute organism, Nosema Bombycis, Nägeli, 
Panhistophyton, Lebert, which accompanies and according to Pasteur’s experiments 
causes the destructive disease in the caterpillar of the silkworm known as pébrine or 
gattine, belongs to this group. It appears in the form of small ellipsoid or somewhat 
elongated peculiarly refractive bodies resembling Bacteria, which may penetrate through 
all parts of the caterpillar and butterfly. We learn from Pasteur that it may find its 

1 v. Heydenreich, Unters. ii. d. Parasiten d. Rückfalltyphus, Berlin, 1877.—Lachmann in 
Deutschen Arch. f. klin. Medicin, 27, p. 52 b. ö 
