110 LEO F. RETTGER 



Fresh meat extract, also, is excellent nutriment for the bac- 

 terial cell. Commercial meat extract, while more uniform in 

 composition than the other, loses much of its richness in the 

 long process of preparation which involves prolonged applica- 

 tion of heat and contact with filters. 



The chemical composition of these more or less unstable 

 but highly nutritive substances is a matter of purest speculation. 

 For want of a better name they may well be termed ''vitamins" 

 or ''accessory growth factors." While some are very unstable, 

 others perhaps will withstand a certain amount of heat, and 

 even rapid steam sterilization. The diphtheria bacillus seems 

 to grow about as well on serum sterilized by the ordinary inter- 

 mittent method as by the process originally advocated. It 

 is a well known fact that Treponema pallidum will grow in 

 ascitic fluid medium which has been sterilized by heat, and 

 that, therefore, extreme precaution to use absolutely uncon- 

 taminated ascitic fluid is unnecessary. That there is danger of 

 too strong application of heat is of course not to be denied. 



The occurrence of vitamins in animal fluids, and probably in 

 vegetable tissues, and their significance in the cultivation of 

 the meningococcus, have received considerable attention by 

 Dorothy Lloyd (1916) in her recent cultural studies of this 

 organism. According to these investigations, primary cultiva- 

 tion of the meningococcus is possible only in the presence of 

 certain accessory growth factors which are present in blood 

 serum and other animal fluids, and probably in vegetable tissues. 

 These accessory bodies are moderately heat stable, and are 

 soluble in alcohol and in water. They are rapidly absorbed 

 from solution by filter paper, but not by glass wool. ^ The 

 vitamins increase the reaction velocity of the proteolytic metab- 

 olism of the meningococcus. After the first or primary arti- 

 ficial cultivation the meningococcus gradually becomes inde- 

 pendent of these substances. Old laboratory strains need no 

 vitamins so long as amino acids are present. The main food 

 requirements are the amino acids. 



Cole and Lloyd (1917) have shown the following to be impor- 

 tant factors in the cultivation of the gonococcus. Suitable H 



