SUMMER DIARRHCEA 165 



TABLE 19. 



Milk- 

 No change 



Alkaline 



Acid, later Alkaline 



Acid 



Acid and Clot ... 



" It will be seen that by adopting such a scheme the characters of an organism can 

 be very easily recorded, for example G a 8 signifies a bacillus producing acid and gas 

 in glucose, but no change in the other fermentable substances. Milk becomes alkaline, 

 indol is produced and the bacillus is motile. 



"This scheme seems to give the greatest differentiation which is possible by means 

 of the media employed. The bacilli composing a sub-group are probably specifically 

 distinct from those composing other sub-groups. To what extent each variety 

 represents a different species is a matter which cannot be decided at present. The 

 varieties within sub-groups which produce no change or an alkaline reaction in milk 

 are probably specifically different from those which produce permanent acidity. The 

 production of acid followed by the formation of alkali is also perhaps a specific 

 character. The capacity to produce indol is possibly a racial character. Undoubtedly 

 the presence or absence of motility is the least important of the differentiating 

 characters. The presence of well marked motility is easily ascertained. On the other 

 hand the absence of motility cannot be so readily determined. In many cultures only 

 a few of the organisms possess motility at the time of examination, and prolonged 

 observations with cultures of different ages may be necessary before it can be definitely 

 seated that the organism in question is non-motile. 



" By the use of a larger number of fermentable substances the bacilli might no 

 doubt be further differentiated, but for the purpose of preliminary examination the 

 method which has been adopted ought to sufiftce until it has been definitely ascertained 

 that some of the bacilli belonging to certain groups possess important pathogenic 

 properties and cannot be differentiated without the use of other media. 



