CHAPTER IV 



THE CHEMISTRY OF BACTERIA AND THEIR 

 PRODUCTS 



STRUCTURE AND PHYSICAL PROPERTIES 1 



IN structure, as in nearly all other respects, bacterial cells 

 stand intermediate between the cells of ordinary plant and ani- 

 mal tissues. Their cell wall seems to be generally more highly 

 developed than that of animal cells, and less so than the wall 

 of most plant cells. In composition, however, the wall is more 

 closely related to animal than to vegetable tissues. The much- 

 vexed question as to the existence or non-existence of a nucleus 

 seems to be best answered by Zettnow, who considers that the 

 portion of the bacterial cell usually made evident by ordinary 

 staining methods consists of a mixture of nuclear substance 

 (chromatin) with non-chromatic substance (entoplasm) the outer 

 membrane, which requires special methods for its satisfactory 

 demonstration, consists of a modified cytoplasm (ectoplasm). 

 Some bacteria consist chiefly of chromatin (e. g., vibrios), but 

 the proportion of the different elements varies greatly, not only 

 in different varieties, but also in the same variety under differ- 

 ent conditions. The fact that the chromatin is not aggregated 

 into the usual nuclear form may be ascribed to the low stage of 

 development reached by bacteria in the scale of evolution ; or, 

 as Vejdovosky has suggested, to the extremely rapid rate of 

 cell division in the bacteria which prevents the chromatin from 

 appearing in the resting stage which a nucleus constitutes. 

 Finer structures within the bacterial cell have as yet been only 

 imperfectly discerned. 



The thickness of the ectoplasm varies greatly even in the same 

 species, being generally greatest in older cultures. In some 

 forms the ectoplasm may constitute one-half of the total mass 

 of the cells. The capsule seems to arise through a swelling of 

 the ectoplasm, and is probably present in at least a rudimentary 

 stage in all bacteria (Migula). 



1 In this chapter references will not generally be given that can be found by 

 consulting Kolle and Wassermann's Handbuch. A general consideration of 

 the Biology of the Bacteria, including references to the effects of light, heat, 

 osmotic pressure, etc., is given by Miiller, Ergeb. der Physiol., 1904 (4), 138. 



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