1913.] 



Variation in Bacillus coli. 



375 



Culture C. 



This was plated out several times at intervals of about two months, but 

 only one type of organism was obtained in every case. This type coagulated 

 milk usually in 48 hours, produced only A., si. G-. in lactose, A., si. G. to 

 + reaction in dulcitol (in 8 to 12 days), + + reaction in glucose and A., si. G. 

 to + reaction in mannitol (in 48 hours). In salicin, acid usually appeared 

 about the 7th day. This variety was quite permanent. Every endeavour 

 was made to restore the original activity of the organism, without success. 



It does not differ markedly from the original culture, but tested side by 

 side the difference is decided. 



Culture D. 



This was the inoculation of Culture C made into Malachite Green 

 broth (0 - 05 per cent.), as stated. It underwent no greater physiological 

 changes than did C, milk did not coagulate until about the 15th day in 

 most cases, and in lactose never more than the A., si. G. reaction was 

 obtained. Physiologically the organism was the same as Culture C and was 

 as permanent ; culturally it showed marked differences. Its power to grow 

 at 20° C. was greatly inhibited. No growth was apparent until six days had 

 elapsed, and then a very watery viscid streak appeared. Growth at 37° C. 

 was quite normal. 



Culture B. 



This organism, on the other hand, became profoundly modified. After 

 several re-inoculations in B.G. broth it was plated out and the colonies 

 obtained on testing in the usual media gave : Milk, acid 48 hours, coagulated 

 in about five days ; lactose, glucose, and mannitol, acid in 48 hours, but no 

 gas at any time ; dulcitol, not attacked at all ; salicin, sometimes acid after 

 several days and sometimes not attacked. Every attempt to restore the 

 original activity failed, the above features being quite permanent. One 

 colony of this type was then started in Malachite Green broth (O'Oo per 

 cent.), in which it soon grew well. 



After several re-inoculations, the colonies, on plating out on agar ( + 1) at 

 20° C, came up very slowly and were watery and very large (|--inch diameter). 

 On testing, acid production was delayed in lactose and mannitol till the 

 5th day, but glucose was rendered acid in 48 hours. Sub-culture on agar at 

 37° C. restored acid production in lactose to 48 hours, but not in mannitol, 

 which was still delayed. Gelatin sub-cultures at 20° C. were rather weaker 

 physiologically than the original culture from which they were taken. 



It must be carefully noted that only changes in physiological activity had 

 occurred. The ordinary growth of all the organisms described above was 



