C0RYNEBACTER1UM DIPHTHERIA. 395 



lonths. Even when dried so that it may be pulverized 

 ito dust, the bacteria remain alive and infectious (Ger- 

 lano). 



(6) Moist heat : They are rapidly killed at 60°, and in a 

 few hours at 50°. 



(c) Cold : When dried, many individuals bear the cold 

 of the German winter for two and one-half months with- 

 out reduction of virulence (Abel); according to Kasansky, 

 cultures endure the Russian winter for months. 



(d) Light : While germs suspended in water are destroyed 

 in a few hours (two to eight hours) by direct sunlight, 

 agar and especially bouillon cultures stand the sunlight 

 for six hours very well. 



Chemical Activities. — (a) Formation of gas and acids 

 from carbohydrates: From grape-sugar, even from the 

 minute quantity found in ordinary bouillon, easily demon- 

 strable acid is produced; also similarly from glycerin. 



The increase of acid produced by typical diphtheria 

 cultures in 5 c.c. of non-saccharine bouillon after twenty 

 hours usually amounts to 1.2-1.5 c.c. of 1 : 40 normal 

 sodium hydroxid; after forty hours, 2.5-3.0 c.c, phenol- 

 phthalein being used as indicator. In 1 % sugar bouillon 

 we found about twice as much acid formed : i. e., 2.6-3.8 

 in twenty hours and about 6.0 in forty hours. Kurth, 

 like Spronck, proposes that 0.2% grape-sugar be always 

 added to bouillon, since he often obtained bouillon which 

 contained too little sugar. 



(6 and c) Production of H 2 S is slight. Indol is always 

 produced. 



(d) In older cultures there is some nitrite, so that the 

 ■ c cholera-red reaction ' ' is obtained with sulphuric acid 

 alone (Palmirski and Orlowski). 



(e) Chromogenesis : Rarely there occur yellow to red 

 cultures. (Zupnik, Frankel. Seep. 405.) 



(/) Toxins: Old bouillon cultures filtered through clay 

 produce symptoms identical with those following inocula- 

 tion of the diphtheria bacillus itself 1 (Roux and Yersin). 



1 The fibrinous exudate alone is lacking at the place of inoculation. 

 Often there occurs albuminuria, diarrhea, and very irregular action of 

 the heart. During the course or after the disappearance of the acute 

 symptoms paralyses occur, especially in the more resistant animals: 



