TAXONOMY 223 



Form of Cell Groups after Cleavage. The individual bacteria 

 after cleavage may separate, or cohere. The amount of cohesion, 

 together with the plane of cleavage, determines the various forms 

 of the cell groups. Thus, among the cocci, diplo- or double forms 

 may result giving rise to distinguishing morphological character- 

 istics. Similarly among the bacilli characteristic forms result 

 as single individuals and others which form chains of various 

 lengths. 



Rapidity of Growth and Multiplication. The rapidity with which 

 bacteria grow and multiply is dependent upon species and environ- 

 ment. The rapidity of the growth is surprising. Under favorable 

 conditions they may elongate and divide every twenty or thirty 

 minutes. If they should continue to reproduce at this rate for 

 twenty-four hours a single individual would have 17 million de- 

 scendants. If each of these -should continue to grow at the same 

 rate, each would have in twenty-four hours more, 17 million off- 

 spring, and then the numbers would develop beyond conception. 

 However, such multiplication is not possible under natural or even 

 artificial conditions, both on account of lack of nutritive material 

 and because of the inhibition of the growth of the bacteria by their 

 own products. If they did multiply at this rate in a few days there 

 would be no room in the world but bacteria. 



Chemical Composition of Bacteria. The quantitative chemical 

 composition of bacteria is subject to wide variations, dependent 

 upon the nutritive materials furnished them. About 80 'to 85 

 per cent, of the bacterial body is water; proteid substances constitute 

 about 50 to 80 per cent, of the dry residue. When these are ex- 

 tracted, there remain fats, in some cases wax, in some bacteria 

 traces of cellulose appear, and the remainder consists of i to 2 per 

 cent. ash. 



The proteids consist partly of nucleo-proteids, globulins, and 

 protein substances differing materially from ordinary proteids. 

 Toxic substances known as endotoxins to distinguish them from 

 bacterial poisons secreted by certain bacteria during the process of 

 growth, also occur. 



