Toxic Products 637 



simulating as nearly as possible those found in nature 

 When buried in the upper layers of the soil the bacilli 

 retain their vitality for nearly six months. Robertson* 

 found that when planted in soil and occasionally fed 

 by pouring bouillon upon the surface, the typhoid bacillus 

 maintained its vitality for twelve months. He suggests 

 that it may do the same in the soil about leaky drains. 



Cold has little effect upon typhoid bacilli, for some can 

 withstand freezing and thawing several times. Observing 

 that epidemics of typhoid fever had never been traced to 

 polluted ice, Sedgwick and Winslowf made some investiga- 

 tions to determine what quantitative reduction might be 

 brought about by freezing, and accordingly experimentally 

 froze a large number of samples of water intentionally in- 

 fected with large numbers of typhoid bacilli from different 

 sources. It was found that the typhoid bacilli disappeared 

 in proportion to the length of time the water was frozen, 

 and that the reduction averaged 99 per cent, in two weeks. 

 The last two or three germs per thousand appeared very 

 resistant and sometimes remained alive after twelve weeks. 



They have been found to remain alive upon linen from 

 sixty to seventy-two days, and upon buckskin from eighty 

 to eighty-five days. 



The typhoid bacillus resists the action of chemic agents 

 rather better than most non-sporogenous organisms. The 

 addition of from o.i to 0.2 per cent, of carbolic acid to the 

 culture-media being without effect upon its growth. At 

 one time the tolerance to carbolic acid was thought to be 

 characteristic, but it is now known to be shared by other 

 bacteria (colon bacillus) . It is killed by i : 500 bichlorid of 

 mercury solutions and 5 per cent, carbolic acid solutions in 

 five minutes. 



Metabolic Products. The typhoid bacillus does not 

 produce indol. It produces a small amount of acid when 

 grown in sugar-containing media, but its regular tendency is to 

 form alkalies, as is shown by the reactions in litmus milk. 

 It forms no coagulating or proteolytic enzymes. 



Toxic Products. The disproportion of local to consti- 

 tutional disturbance in typhoid fever and the irritative 

 and necrotic character of its lesions suggest that we have 



* "Brit. Med. Jour.," Jan. 8, 1898. 



f"Jour. Boston Soc. of Med. Sci.," vol. iv, No. 7, p. 181, March 

 20, 1900. 



