INFECTIONS OF THE DIGESTIVE TRACT 165 



stances made by the bacilli. It is quite aside from the 

 present design to discuss problems of immunity, but it 

 is perhaps desirable to note certain facts relative to 

 the protective action aroused by typhoid bacilli. The 

 experimental inoculation of human beings with typhoid 

 cultures exposed to heat has been shown by Wright to 

 result in the following changes in the blood; (1) an in- 

 crease m the bactericidal power of the blood; (2) an 

 increase in bacterioly tic power of the blood ; (3) a devel- 

 opment of antitoxic properties as indicated by the miti- 

 gation of the severe constitutional signs of intoxication 

 that ordinarily follow a first inoculation with typhoid 

 vaccine; (4) an increase in the ability of the leucocytes 

 to take up and digest typhoid bacilli ; and (5) the devel- 

 opment of specific agglutinating powers of the blood for 

 typhoid bacilli. With the exception of the agglutinating 

 action of the blood, which bears no definite relation to the 

 immunity of the patient, conditions similar to these 

 apparently constitute at least a part of the mechanism 

 of defense hi the case of typhoid fever. How far the 

 bactericidal property of the blood as measured in vitro 

 is an evidence of effective bactericidal activity within 

 the body is an open question. Bail emphasizes the fact 

 that an experimental immune serum which is active 

 outside the body, does not cause an effective solution 

 of typhoid bacteria when injected with such bacteria 

 into the blood stream. The antitoxic power noted by 

 Wright is very likely dependent on "anti-aggressins" 

 that have arisen in response to "aggressins." Effective 

 "anti-aggressin" action is probably extremely important 



