24 BIOLOGY AND TECHNIQUE 



grown on broth or on a protein-free synthetic medium, and concludes 

 that bacteria are capable of building up their own protein, independ- 

 ent of the nature of their food supply. 



Although there is much uncertainty about the nature of the 

 relatively thermostable toxic substances contained in bacteria, the 

 endotoxins, it is probable that they are also of protein nature. 



The fats, which are demonstrable both by michrochemical 

 methods, staining with Sudan III, Scharlach R., and Osmic acid, 

 and by alcohol-ether extraction, consist of fatty acids, true fats, and 

 in the case of the tubercle bacillus, at least, of waxy substances. 33 

 The acid-fastness of these organisms is probably due in part to the 

 presence of these lipoidal constituents, which are present to the 

 extent of 20 to 40 per cent of the dry weight of the bacteria. 



Cellulose has been stated to occur in certain species of bacteria, 

 but the evidence is unsatisfactory and many investigators have failed 

 to recognize it. A hemicellulose has also been described by Nishi- 

 mura 34 and by Tamura. 35 Chitin, the shell-like material making 

 up the protective covering of lobsters, crabs, insects, etc., seems to 

 have been definitely recognized in bacteria, by Iwanoff, 36 who ob- 

 tained considerable quantities of glucosamine hydrochloride from the 

 hydrolysis of his preparation. The occurrence of chitin in bacteria 

 would seem, again, to connect these organisms more closely to the 

 animal than to the vegetable kingdom, thus contradicting the rela- 

 tion suggested by the split products of the nucleic acid. 



Glycogen-like substances have been demonstrated, according to 

 A. Fischer 37 in B. subtilis and B. coli. These bacteria stained a red- 

 dish brown with iodin, and after treatment with weak acids were 

 shown to contain dextrose. Hydrolysis of other bacteria has given 

 reducing sugars, resulting presumably from the decomposition of 

 mucins and perhaps of gums. 



The bacterial ash consists largely of phosphates and chlorides of 

 potassium, sodium, calcium and magnesium. The phosphate prob- 

 ably occurs for the most part as a constituent of the nucleic acid. 

 Certain of the higher bacteria also contain iron oxide in granular 



33 De Schweints and Dorset, Cent. f. Bakt., Erste Abt., xxii, 1897, 209. 



34 NisJiimura, Arch, f . Hyg., xviii, 1893, 318 and xxi, 1894, 52. 



35 Tamura, Zeit. f . physiol. Chemio, Ixxxix, 1914, 304. 

 Iwanoff, Hofmeister's Beitr., 1, 1902, 524. 

 '"Fischer, A., "Vorlesung iiber die Bakt.," Jena, 1903. 



