TYPHOID FEVER. 257 



through sewage. The bacillus probably enters milk oc- 

 casionally in water used to dilute it. 



The resistant powers of the organisms have already 

 been described as great. They can grow well at the 

 room-temperature. The thermal death-point is given by 

 Sternberg as 60 C. The bacilli can, according to Klem- 

 perer and Levy, remain vital for three months in distilled 

 water, though in ordinary water the commoner and more 

 vigorous saprophytes outgrow them and cause their dis- 

 appearance in a few days. When buried in the upper 

 layers of the soil the bacilli retain their vitality for nearly 

 six months. Cold has no effect upon the typhoid bacilli, 

 for freezing and thawing several times are without injury 

 to them. They have been found to remain alive upon 

 linen for from sixty to seventy-two days, and upon buck- 

 skin for from eighty to eighty-five days. Sternberg has 

 succeeded in keeping hermetically-sealed bouillon cul- 

 tures alive for more than a year. In the presence of 

 chemical agents the bacillus is also able to retain its 

 vitality, o. i to o. 2 per cent, of carbolic acid added 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. 



Cultures of the typhoid bacillus may be obtained, but 

 with difficulty, from the alvine discharges of typhoid 

 patients. In examining this material, however, it must 

 be remembered that the bacilli are certain to be present 

 only in the second and third weeks. 



As numerous saprophytic bacteria are present in the 

 feces, the resistance which the typhoid bacillus exhibits 

 to carbolic acid can be made use of in obtaining the pure 

 culture. To each of several tubes of melted gelatin 0.05 

 per cent, of carbolic acid is added. This addition is most 

 easily calculated by supposing the average amount of 

 gelatin contained in a tube to be 10 c.cm. To the aver- 

 age tube y 1 ^- c. cm. of a 5 per cent, solution of carbolic acid 

 is added, and gives very nearly the desired quantity. A 



17 



