CHAPTER XI. — MODE OF LIFE OF 7' HE BACTERIA. 48 1 



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 parasites, 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 oxidations, 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 

 fermentations, lactic acid fermentation, butyric acid fermentation and the viscous 

 fermentation of sugar, &c, they also act as inciters of putrefactive 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 

 destructive 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 parasitic on plants have scarcely ever been observed, a fact to which 



1 Pasteur in Comptes rend. 54, p. 265, and 55, p. 28. — Nageli, Theorie d. Gahrung, p. III. 



2 See Koch, Mittheil. d. Reichsgesundheitsamts, I, p. 61. 



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