1 88 PHYSIOLOGY OF MICROORGANISMS 



incorporate an amount which is difficult to remove and which has 

 some relation apparently to their high degree of resistance. 



Molds have, as a rule, a greater moisture content than yeast and 

 yeast a greater content than bacteria, yet these organisms have no 

 constancy or uniformity in their moisture content. The protozoal 

 forms are as dissimilar as others and their range of moisture content 

 assumes no fixed boundaries. 



Although there is a minimum limit and a maximum limit as indi- 

 cated on the one hand by desiccation and on the other hand by an 

 inability to absorb more moisture, still retaining life one is forced to 

 believe in a very restricted amount of moisture as essential to life- 

 processes. Beyond this essential amount, in the case of too little, the 

 metabolic activities cannot take place, and, in the case of an excessive 

 amount, proper functioning is interfered with or a modification of 

 physiological reactions gradually becomes more and more evident. 



Proteins and other nitrogenous substances. Nitrogenous compounds 

 are present in varying amounts and are assumed to be the basis of 

 protoplasm. The approach in the study of this class of substances 

 has been made through the determination of nitrogen, then converting 

 the nitrogen into terms of protein by the use of the recognized factor; 

 by the recognition of definite nitrogenous compounds which may 

 represent certain portions of the protein molecule; and by the use of 

 reagents long employed to detect the presence of protein, largely 

 qualitatively. All of these can furnish only inadequate means for the 

 recognition of the nitrogenous materials which may enter into the 

 formation of the active life-substance, protoplasm. However limited 

 may be the knowledge available in this particular subject, there is now 

 at hand sufficient to point the way for more and for certain directive 

 practical purposes. The per cent, of nitrogen * found by Vaughan and 

 his associates and by Nicolle and Alilaire ranges from 3.96 (dry weight, 



* Vaughan and Wheeler. "Protein Split Products in Relation to Immunity and Disease," 

 by Vaughan, contributes the nitrogen determinations in per cent, for several bacteria: Typhoid, 

 11.55; colon, 10.65; tuberculosis, 10.55 ; anthrax, 10.285; subtilis, 5-964; Proteus vulgaris, 6.791; 

 Ruber of Kiel, 10.655 ; megaterium, 8.349; pyocyanus, 10.843; violaceus, 11.765; Sarcina 

 aurantiaca, 11.46. 



Nicolle, M., and Alilaire, E., in Ann. liist. Pasteur, 23, 555, give the following nitrogen re- 

 sults in per cent, (based upon dry weight), Bact. mallei, 10.47; Bad. cholera gallinarum, 10.79; 

 Msp. comma (Bombay), 9.79; Bact. dysenteries (Shiga), 8.89; B. proteus (Proteus vulgaris), 

 10.73; B. typhosus, 8.28; Bact. anthracis (asporogenic) , 9.22; Bact. pseudotuberculosis, 10.36; 

 Bact. pneumonias, 8.33; B. coli, 10.32; B. prodigiosus (pathogenic) (de Fortineau), 10.55; B. 

 psittacosis, 9.55; B. pyocyaneus, 9.79; B. lymphangitis (de Nocard), 9.17; yeast (Frohberg), 

 10. oo; Chlorella vulgaris, 3.96. 



