108 CHEMISTRY OF BACTERIA AND THEIR PRODUCTS 



Bulloch and Macleod found that ethereal extracts did not con- 

 tain the acid-fast substances which they consider to be a wax-like 

 alcohol, soluble in hot, but insoluble in cold absolute alcohol or 

 in ether. The simple fats seem to be formed by oleic, isocetinic, 

 and myristinic acids, and there is some lauric acid in the form of 

 a soap. Cholesterin is probably present, and there are also 

 lipochromes giving the cultures their color. 



By staining with sudan III, Sata l demonstrated fats, not 

 only in the acid-fast bacilli, but also in anthrax, Staphylococciis 

 aureus, B. mucosus, and actinomyces ; but not in diphtheria, 

 pseudo-diphtheria, plague, cholera, and chicken cholera bacilli, 

 or in members of the colon group. 2 Only a few bacteria form 

 fat on agar free from glycerin, but potato is a favorable medium. 



Spores differ from their parent bacteria in containing a much 

 greater proportion of the solid constituents and less water. In 

 molds Drymont found that the spores contained over 60 per 

 cent, of dry substance, and almost all the water was so held as 

 to resist drying by temperatures below boiling ; the dry sub- 

 stance is very rich in proteid and poor in salts. The wall of 

 the spore consists of a " cellulose-like " substance (probably 

 chitinous) and a very hygroscopic extractive matter. The great 

 resistance of spores to drying and to heat can be readily under- 

 stood in view of these facts. Flagella also seem to be composed 

 of a relatively condensed proteid. 



Staining 1 Reactions. The staining reactions of bacterial 

 cells are much as if the bacteria consisted entirely of chromatin, 

 so that at one time the theory prevailed that bacteria consisted 

 merely of a nucleus and a cell wall, without any true cytoplasm. 

 The demonstration of abundant nucleoproteid in the contents of 

 bacterial cells explains their staining affinity for basic anilin 

 dyes. Owing to some unknown differences in composition, not 

 all bacteria are stained equally well by the same basic dyes. 

 Although the staining of bacteria depends upon a chemical re- 

 action between the nucleoproteids and the basic dye, yet the 

 combination is not usually a firm one, being readily broken by 

 weak acids in most cases. That the decolorization of bacteria 

 depends upon dissociation of the dye-proteid compound is shown 

 by the fact that absolutely water-free alcohol will not decolorize 

 dry bacteria, nor do water-free alcoholic solutions of dyes stain 

 dehydrated bacteria. 



1 Cent. f. allg. Path., 1900 (11), 97. 



2 Auclair (Arch. He'd. Exper., 1903 (15), 725) contends that the ether and 

 chloroform extracts of many pathogenic bacteria contain important toxic sub- 

 stances. Holmes (Guy's Hosp. Reports, 1905 (59), 155) states that injection 

 of fatty acids from tubercle bacilli into rabbits causes a lymphocytosis. 



