TEXT-BOOK OF BACTERIOLOGY. 393 



larly and luxuriantly, while most other micro-organisms fail, espe- 

 cially if there was added to the " potato gelatin " about 0.05^ of 

 carbolic acid, or if the culture apparatus had been treated with 

 phenol by Thoinot's method. Finally', Kitasato's observation should 

 be mentioned, which is also designed to facilitate the finding of 

 typhus bacilli. They differ from other similar bacteria by not 

 yielding the red indol reaction (as the cholera bacteria do) on 

 the addition of nitrite of sodium (1 c.cm. of a solution containing 

 0.03 in 100 c.cm. to 10 c.cm. of the culture fluid) and a few drops of 

 concentrated sulphuric acid. 



The growth of the typhus bacillus on gelatin, potatoes, etc., 

 shows that it is not an absolutely parasitic micro-organism. Be- 

 sides the media before mentioned, it also thrives on other sub- 

 stances, mostly of vegetable nature; for instance, on decoctions of 

 marsh-mallow, carrot-juice, etc. 



Wolflhiigers observation that milk is an excellent medium for 

 their development and that they live or even increase in water is 

 very important as bearing upon the possible distribution of the bac- 

 teria. It harmonizes in many respects with tlie statements made 

 during late years as to the discovery of typhus bacilli in suspicious 

 drinking-water, and consequently their occurrence outside of the 

 human body. 



Does the micro-organism designated by us as " typhus bacillus " 

 actually give rise to the affection expressed by its name ? 



It is not found in all cases of typhus, and thus far we have by no 

 means succeeded in proving its existence without exception in every 

 part of the body afflicted. But this maj'^be owing to certain defects 

 in investigation — for instance, the failure of a specific staining proc- 

 ess — or to some peculiarities of distribution and arrangement of the 

 rods in the tissue. If we consider that these bacilli have as yet 

 never been met with in any other affection except typhoid fever, 

 we must feel justified in considering the bacteria the cause of the 

 disease. 



A conclusive proof by means of transmission could not be ex- 

 pected, since it is known that typhoid fever, under ordinary con- 

 ditions, never occurs in animals. This difficulty was supposed for 

 a time to have been overcome (as in cholera). 



E. Fraenkel and Simmonds injected into the auricular vein of 

 rabbits dilutions of typhus culture. About one-half of the animals 

 died after twenty-four to forty-eight hours. The spleen, mesen- 

 teric glands, and the follicles of the intestines were swollen; bacilli 

 could always be found in the first-named place, but they had not 

 generally passed into the intestine. 



