MORPHOLOGY, REPRODUCTION, ETC. 21 



few microorganisms indeed, in which prolonged cultivation on artificial 

 media or other unfavorable influences do not produce variations from 

 the ground type which may often make the cultures morphologically 

 unrecognizable. In the case of many of the spirilla (spirillum Milleri, 

 spirillum Metchnikovi, etc.) the degeneration forms may appear within 

 so short a time as two or three days after transplantation. 



CHEMICAL AND PHYSICAL PROPERTIES OF THE BACTERIAL CELL 



Chemical Constituents. The quantitative chemical composition of 

 bacteria is subject to wide variations, dependent upon the nutritive 

 materials furnished them. 



Approximately 80 to 85 per cent of the bacterial body is water. 

 The remainder consists chiefly of proteids which constitute roughly from 

 50 to 80 per cent of the dry substances. Remaining, after extrac- 

 tion of these, are fats, and in some cases true wax (fatty acid combina- 

 tions with higher alcohols), traces of cellulose (in some bacteria only), 

 and the ash which makes up usually about 1 to 2 per cent of the dry 

 substances. 



The extensive researches of Cramer 1 have shown how widely at va- 

 riance quantitative analyses may be when made of cultures of the same 

 species of bacteria grown upon different media. Thus the dry sub- 

 stances of the cholera vibrio were found to be made up of 65 per cent 

 of proteids when the microorganisms were grown upon nutrient brqth 

 as against 45 per cent when the same bacteria had been grown upon 

 the proteid-free medium of Uschinsky. Analyses made by Kappes 2 of 

 B. prodigiosus and by Nencki 3 and Schefferof some of the putrefactive 

 bacteria, may serve to illustrate the approximate proportions of the 

 substances making up the bacterial body. 



B. Putrefactive 



prodigiosus Bacteria 



Water 85 . 45 per cent. 83 . 42 per cent. 



Proteids 10.33 " " 13.96 " " 



Fats 0.7 " " 1. " " 



Ash 1.75 " " 0.78 " " 



Residue .. . 1.77 " " 0.84 " " 



1 Cramer, Arch. f. Hyg., xii, xiii, xvi, xxii, xxviii. 



2 Kappes, " Analyse der Massenkulturen," etc. Diss., Leipzig, 1889. 

 8 Nencki und Scheffer, Jour. f. prakt. Chemie, new ser. xix, 1880. 



