CHAPTER XI.—MODE OF LIFE OF THE BACTERIA. 481 
Section CXXXVI. The Bacteria, apart from the forms which contain chlorophyll 
and which have not yet been carefully studied, are distinguished according to their 
actual vegetative adaptation into saprophytes and paraszies, in the sense in which the 
words were employed in section XCIX. 
The adaptation of the saprophytic forms presents the same general points of 
view as that of the saprophytic Fungi. Many Bacteria are, like these Fungi, to some 
extent organisms which produce oxidarions, combustions of the substratum. The 
Micrococcus of vinegar or mother of vinegar (Arthrobacterium aceti, Mycoderma 
aceti) oxidises ethyl alcohol in atmospheric air and converts it into acetic acid; but 
it may also convert it by combustion into carbonic acid and water’. Bacillus subtilis 
and as it would appear B. Megaterium also cause similar combustion of organic com- 
pounds and produce carbonic acid and water. Many others excite characteristic 
JSermentations, lactic acid fermentation, butyric acid fermentation and the viscous 
fermentation of sugar, &c., they also act as inciters of pusrefactive processes. For the 
details of these phenomena, which are the subject of so much discussion at the present 
day, the reader is referred to the special literature of the Bacteria and of the chemistry 
of fermentation, to the excellent researches of A. Fitz especially, and those of Nageli 
and Duclaux, and to Pfeffer’s Physiologie, I, chap. 8. 
Many Bacteria on the other hand are parasitic in and on living organisms. 
In the determination and description of their mode of life the same points of view 
must be taken, and the same divisions and nomenclature applied, as those which were 
explained at length in connection with parasitic Fungi in speaking of their relations to 
their host and the effects they produce in it, for the same or quite analogous 
phenomena occur in both cases. In the succeeding remarks therefore there is a tacit 
reference throughout to sections CI-CXIII. 
All parasitic Bacteria live as endophytes in the cavities of the body or in the 
substance of the tissue of the host. Their structure and growth determine the mode 
in which they attack the host; they find their way either as spores or in the vegetative 
form into normal cavities of the body accessible from without or into wounds, and in 
both places they continue a process of vegetation ; they may also be passively conveyed 
from wounded surfaces in the bodies of animals into the blood and lymphatic passages, 
or else they penetrate into the cells and tissue from any surface to which they have 
been conveyed. The Bacillus of anthrax for instance penetrates into the mucous layer 
of the intestinal canal 2, when it has been carried to it in the animal’s food. The 
effects of fermentation will have something to do with the perforations thus produced, 
and the direction of the movement will depend on the co-operation of the chemical 
and physical qualities of the substratum and possibly of the spontaneous motion of 
the parasite. 
All known parasitic Bacteria are simply and for the most part vigorously 
destruchve in their effect upon their host, if we do not in their case also reckon 
inflammatory processes (the formation perhaps of tubercles) among phenomena of 
diseased growth and new formation. 
Bacteria parasitie on plants have scarcely ever been observed, a fact to which 

1 Pasteur in Comptes rend. 54, p. 265, and 55, p. 28.—Nägeli, Theorie d, Gährung, p. III. 
2 See Koch, Mittheil. d. Reichsgesundheitsamts, I, p. 61. 
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