318 KAN-ICHIRO MORISHIMA 



Here Cohen S is very agglutinable in the presence of hydro- 

 chloric acid, although it is not so in the presence of acetic acid, 

 as we have seen in Michaelis' test. Michaelis himself used only 

 acetic acid. 



SUMMARY AND CONCLUSIONS 



In the study described above we have endeavored to investigate 

 the variations which may occur in the characteristics of typical 

 typhoid bacilli in regard to their abilities to utilize carbohydrates, 

 and their behavior to serum antibodies under various conditions 

 of cultivation. Underlying our plan of experimentation was the 

 purpose of determining whether variations noted by others and 

 described in many published accounts could properly be regarded 

 as mutations in the botanical sense, and, secondarily, to con- 

 tribute to the comprehension of the nature and the permanence 

 of variations from type so often noticed in freshly isolated 

 cultures, incidentally thereby shedding some light upon the prac- 

 tically difficult problems so often encountered by the bacteri- 

 ologist in the identification of strains isolated from the human 

 and animal body. 



In order to obtain a true picture of the fermentative character- 

 istics of a gi\'en species of bacterium it is clear from the foregoing 

 study that the inoculation of a rather small number of strains 

 into fluid media containing the various sugars and the recording 

 of acid and gas production after a few days' incubation is entirely 

 inadequate. A large number of strains must be investigated 

 and the period of observation extended to thirty days, if neces- 

 sary. Furthermore, it seems advisable to regard "fermentation" 

 not as the production of gas and acid or even as the production 

 of acid from the sugar by the bacterium, but simply as the 

 utilization of the sugar as a food by the bacterium. Fermen- 

 tation in this sense is demonstrated quite conclusively on agar 

 plates if characteristic daughter colonies appear on the agar 

 containing the sugar and no daughter colonies appear on control 

 plates of the same agar without the sugar; precisely those cul- 

 tures that yield unsatisfactory results in broth containing the 

 sugar are apt to give rise to a well marked development of 



