CHEMICAL COMPOSITION. 29 



ordinary means. The beginner will often mistake involu- 

 tion forms for contaminations. Plate cultures soon deter- 

 mine whether one or more forms of bacteria are present. 



B. Chemical Composition of Bacteria. 



Qualitatively considered, the bodies of bacteria^ consist 

 in great part of water, salts, and albuminous bodies ;2 



in lesser quantity are present extractive substances soluble 

 in alcohol, and others soluble in ether (triolein, tripal= 

 mitin, tristearin, lecithin, cholestearin). In tubercle 

 bacilli Aronson found in the ethereal extractive (25% of 

 the dry substances), besides free fatty acids, large quan- 

 tities of wax, whose alcohol differs from cholesterin. In 

 no variety of bacteria could E. Cramer find grape=sugar, 

 although many varieties (Bacillus butyricus, varieties of 

 leptothrix) contain starch=like masses, turning blue with 

 iodin. True cellulose was found by Dreyfuss in B. sub- 

 tilis and a bacillus resembling the B. coli; also, the Myco- 

 bacterium tuberculosis forms cellulose in the animal body. 

 The vinegar-forming Bact. xylinum produces such a quan- 

 tity that visiting cards have been made from it as a curi- 

 osity. From cultures of Myc. tuberculosis and a "capsule 

 bacillus from water" resembling the B. pneumonia of 

 Friedlander, on the contrary, no cellulose was obtained, 

 but instead there was found abundant mucoid carbo- 

 hydrates, CgHioOg, closely resembling hemicellulose/ 

 (For literature, ' see Nishirnura, A. H. xvin, 318, and xxi, 

 52). Scheibler (Chem. Centralbl. xi, 181) has described the 

 mucus-like material of the Streptococcus mesenterioides as a 



'H. Buolmer has directed that the cell-contents (bacteria proto- 

 plasm) be obtained by trituration and the hydraulic press (3 to 500 

 atmospheres). Compare Hahn (C. B. xxili, 86). 



^Albumin and salts can constitute as much as 98% of the dry bodies 

 of bacteria (Vibrio cholerse); on the contrary, as much as 12% of 

 carbohydrates may be present in the capsules. In bacterial albumin 

 Hellmich recognized a globulin (Arch. f. exp. Pathol, u. Pharmak. 

 XXVI, 345). Most improbable appears the statement of Fermi that 

 he has grown nitrogen-free ( ! ) micro-organisms (C. B. L. il, 505) . 



