CHEMICAL COMPOSITION OF THE CELL 53 



Ncncki (27) isolated the protcid constituents of the bacterial cell by pre- 

 cipitation with boiling hydrochloric acid, removal of fats with ether and 

 alcohol, solution in caustic potash and final precipitation with chloride of 

 sodium. The substance thus obtained (mycoprotein\ agrees pretty closely 

 in composition with one prepared by Schlossbcrger from yeast, and contains 

 52-39 per cent, carbon, 7-55 per cent, hydrogen, 14-75 P cr ccnt - nitrogen, 

 and about 25 per cent, oxygen. Even if we assume that this body (free 

 from sulphur and phosphorus) is an unaltered constituent of the bacterial 

 cell and not a decomposition product from more complex proteins, it is 

 not necessarily the essential constituent of the protoplasm. If it were we 

 should have to place the bacteria chemically as well as morphologically 

 below all other organisms, where, as far as we know, the phenomena 

 of life are inseparably bound up with the presence of highly complex 

 bodies like nuclein and nucleo-albumen rich in phosphorus. Since, how- 

 ever, such compounds do undoubtedly occur in some bacteria, further 

 investigations are necessary before we can form an opinion as to the nature 

 and importance of mycoprotein. 



Closely related to the proteid bodies (using the word in its widest sense) 

 are those poisonous substances known as toxalbumines. The constitution 

 of their molecule is, however, as yet quite unknown*. 



Carbohydrates are probably present in all bacteria, but they certainly 

 do not play such an important part as in the cells of higher plants, for, as 

 already mentioned, the cell-membrane of bacteria consists not of cellulose 

 but of a proteid substance. Apart from the not very clear indications 

 afforded by the 'granulose reaction' in some few species (p. 13) there are 

 no instances of differentiated carbohydrate cell-contents. 



The gelatinous substance produced by Leuconostoc (see p. 10) and 

 by some of the mucilaginous species that occur in wine and beer is probably 

 a carbohydrate (dextrane, [C G H 10 O 5 ] n ) similar to cellulose and the slimy 

 secretions of some gelatinous algae. As special temporary cell constituents 

 must be regarded also those products of fermentation which, although 

 formed in the cell, are not stored up but excreted as metabolic products (see 

 Chaps. XI-XIV). The percentage of ash given in the various analyses of 

 bacteria cannot be taken as indicating in any degree the value of salts in 

 the economy of the cell, because the nutritive media were not prepared with 

 this end in view. 



Food Stuffs of Bacteria (28). 



Mineral substances are as necessary for the Bacteria as for all other 

 organisms, albeit in a much smaller quantity. One milligram of living 

 bacteria (i. c. about thirty milliards of individuals) with I per cent, of ash 



* For the relations of the toxalbumines to infectious diseases, see Chap. XVII. 



