INFECTIONS OF THE DIGESTIVE TRACT 163 



the way has been prepared by poisons which neutralize 

 the defensive substances of the host; for example, by 

 "aggressins." The bacilli of typhoid fever and of cholera 

 may be classed as hemiparasites, and their virulence 

 appears to stand in a close relation to the efficiency of 

 their "aggressins." 



The ordinarily accepted view that the portal of infec- 

 tion for the inciters of typhoid fever is the digestive 

 tract is doubtless true in general and still it may not 

 represent the whole truth. There is some evidence to 

 support the idea that at times the bacilli enter by way 

 of the throat, for the organisms have been found in the 

 tonsil, and a patient may be in the early period of the 

 disease without showing the presence of the bacilli in 

 the stools even when modern methods of isolation are 

 employed. It is conceivable that typhoid bacteria in 

 the intestine do not necessarily point to an original 

 intestinal invasion, as they may at times come mainly 

 from ulcerated Peyer's patches in which the bacilli 

 have accumulated as a result of the invasion of these 

 lymphatic structures in the course of a general bacillary 

 infection which strongly tends to implicate the lym- 

 phatics. It would be of special interest to know whether 

 the axillary and other lymph nodes at a distance from 

 the intestine are early invaded in typhoid fever. Even 

 where the invasion is by the intestinal path the typhoid 

 bacilli, which tend to be irregularly distributed in the 

 intestinal contents, may perhaps come from ulcerated 

 Peyer's patches which have become infiltrated and ulcer- 

 ated, secondarily to the typhoidal bacilla3mia. We should 



