l8o BACTERIA 



disorders favor infection. Death may be due to toxaemiaor ex 

 haustion. As a causal agent in the production of summer diarr- 

 hoeas of children, the dysentery bacillus plays a part, it has 

 been isolated from the stools of infants, with this disease, and 

 their sera have been found to agglutinate the bacilli. Never- 

 theless it is known that other bacteria (streptococci, etc.) cause 

 this disease, and Weaver found that "clinically twenty-four of 

 our ninety-seven cases of ileocolitis in which dysentery bacilli 

 were discovered did not differ from cases in which dysentery 

 bacilli were not found. 



Immunity. The sera from convalescents from dysentery show 

 a strong bactericidal action. Anti-bodies are developed by in- 

 fection and by artificial inoculation with killed cultures. Kruse 

 obtained a serum from horses which strongly protected a guinea 

 pig against a lethal injection of bacilli. The protective property 

 of the serum is due to its bactericidal action. Here the ambo- 

 ceptors act, but only in the presence of a complement. It is 

 possible that a small amount of anti-toxin is present since there is 

 some reason to think that a modicum of free toxins is produced 

 by the bacilli. 



Vaccination. Shiga tried to induce (i) passive and (2) active 

 immunity in many individuals by injecting both anti-toxic serum 

 and bacteria into them. This was not followed by a lowered 

 number of infections, but by a lowered mortality. A serum may 

 be produced by injecting horses with several dysentery strains, 

 called a polyvalent anti-serum. This has good therapeutic effects 

 but does not immunize prophylactically. 



Agglutination. The serum from a patient suffering from either 

 dysentery or summer diarrhoea, will, after about a week's illness, 

 agglutinate bacilli. This property is not always present, and 

 its absence does not exclude the possibility of infection. In 

 performing the reaction, both Shiga's and Flexner's type of 

 organism should be used. These types probably bear the same 

 relation to each other that typhoid and paratyphoid do. 



