VARIATIONS IN TYPHOID BACILLI 293 



1. Arahinose. Thirty-three strains plated on this medium. The 

 daughter colonies appear in two to ten days, each colony usually con- 

 taining many daughter colonies; a few of the daughter colonies fre- 

 quently developed into large flat, deep blue colonies; all of the strains 

 tested gave rise to daughter colonies. 



2. Dextrin. No daughter colonies appeared. 



3. Glucose. Colonies were smaller and denser than on other plates 

 or control plates and no daughter colonies appeared. 



4. Dulcitol. We plated forty cultures and daughter colonies appeared 

 within two to five days. One or two opaque brownish yellow daughter 

 colonies in a mother colony in succeeding days would grow so rapidly 

 in size that sometimes the mother colony would be entirely covered. 

 Furthermore, there is a tendency toward color reduction as the growth 

 increases. 



5. Galactose. Colonies were smaller than on control plain plates and 

 no daughter colonies were produced. 



6. Glycerol. We used 3 per cent glycerol plates for this purpose 

 and obtained colonies which were very thick, opaque and yellowish 

 brown in color. Plates containing China blue produced pale colonies 

 on the first day, which became deep blue later. The color was reduced 

 by the thick growth. No daughter colonies developed. 



7. Inosite. No daughter colonies. 



8. Lactose. No daughter colonies were seen. 



9. Mannitol. No daughter colonies developed. 



10. Maltose. There was good growth in point of size and thickness, 

 but no daughter colonies were visible. Twenty strains were plated. 



11. Raffinose. No daughter colonies developed, but ten days later, 

 they showed papilliform colonies which did not increase in size nor in 

 thickness on further incubation. 



IS. Rhamnose. All thirty typhoid strains which we tested on 1/10 

 per cent rhamnose plates gave rise to daughter colonies as well as on 1 

 per cent rhamnose plates. On the latter and on 2 per cent and 3 per 

 cent plates, we could see many large opaque brownish yellow colonies 

 scattered here and there with small daughter colonies and 1 per cent 

 rhamnose Endo plates showed the same appearance. 



The best method thus far developed for isolating typhoid bacilli from 

 stools consists in plating upon a lactose medium containing brilliant 

 green and an indicator for acid production. It seemed that a further 

 improvement would be introduced by supplying a positive character- 

 istic to the typhoid colonies instead of relying solely on the absence 



