TYPHOID FEVER. 169 



bacilli bear cold quite well ; they are not injured by freez- 

 ing for two or three times, and subsequent thawing. They 

 are less resistant to heat, as has been mentioned. (See 

 Spore-formation.) 



Dried in a thin layer, typhoid-bacilli have been found to 

 preserve their vital activity (Uffelmann) 



In garden-soil for twenty-one days. 



In sweepings for more than thirty days. 



In white filter-sand for eighty-two days. 



Upon linen for from sixty to seventy-two days. 



Upon buckskin for from eighty to eighty-five days. 



Upon wood for thirty-two days. 



According to Kruse, they die in thin layers, dried, with- 

 in from five to fifteen days. 



Portals of Infection and Dissemination of Typhoid- 

 bacilli. Dried typhoid-germs may be carried through the 

 air with floor-dust, street-sweepings, particles of clothing, 

 etc. They may, thus, possibly be inhaled. Infection by 

 way of the lungs, however, is rather improbable with regard 

 to typhoid fever, although it played an important part 

 in the earlier theories that denied the transmission from 

 case to case, and considered necessary the presence of the 

 typhoid-bacilli in the earth for their complete maturation; but 

 this has not been demonstrated. Besides, in human beings 

 the digestive tract appears to be the only portal of entry for 

 the typhoid-bacillus. The typhoid-germs must be swal- 

 lowed, and gain entrance into the intestine. To this end 

 it is necessary that they lodge upon, and be taken up with, 

 food. Apparent infection through the lungs may also be 

 so interpreted that the typhoid-germs contained in dust 

 and with this inhaled are restrained in the upper part of 

 the respiratory tract, to be subsequently carried with food 

 into the digestive tract. It is an important fact that the 

 typhoid-bacillus is not destroyed with certainty by the 

 hydrochloric acid of the gastric juice. The barrier inter- 

 posed by the stomach thus fails to afford reliable protection 

 against typhoid infection, even when the function of that 

 organ is completely normal. 



Articles of food may be contaminated with typhoid-bacilli 

 through the intermediation of the air ; dust containing 

 typhoid-bacilli may be deposited upon articles of food. 

 More frequent, however, is direct contamination by means 

 of the feces, which become attached to the hands of the at- 



