166 INFECTIONS OF THE DIGESTIVE TRACT 



in the struggle betwee^ the organism and the bacteria ; 

 for if the latter cannot restrain the natural protective 

 forces of the animal they are attacking, they cannot 

 efficiently multiply, and they ultimately fall a victim 

 to the action of the leucocytes. During convalescence, 

 after the subsidence of fever, the typhoid bacilli found in 

 the urine can hardly represent bacteria that are multi- 

 plying in the blood and tissues, but rather are micro- 

 organisms that have come from the intestine from cer- 

 tain foci in the tissues and have escaped the action of the 

 leucocytes and bactericidal serum. A state of balance 

 between opposing forces then exists, and this may be 

 readily disturbed to the detriment of the host by factors 

 favoring multiplication of the bacilli in the intestine 

 (such as improper food) or checking the formation of 

 "anti-aggressins." It is a noteworthy peculiarity that 

 a patient may harbor the inciters of typhoid or cholera 

 in the intestine and still not develop the specific disease. 

 The blood in these persons need not contain an increase 

 in bactericidal substances, and this suggests that the 

 individual in question has acquired a local immunity 

 implicating the intestinal structures, which prevents the 

 invasion of typhoid bacilli. Wassermann and Citron 

 have shown that immunity substances are made in 

 connective tissues as well as in the lymphatic system, 

 spleen, and bone marrow, and furnish evidence pointing 

 to the possibility of inducing a local intestinal immunity. 1 



1 For a review of the recent literature relating to typhoid fever, 

 see Kolle and Wassermann's " Handbuch d. path. Mikroorganis- 

 men," Supplementary Volume I, 1906; Kutscher, "Abdominal- 

 typhus," pp. 251, 255, 269, etc. 



