THE AERTRYCKE BACILLUS 



441 



increased virulence, after being heated at 57 C. for an hour to destroy any 

 organisms present therein, is sufficiently virulent to cause the death of normal 

 rabbits in 3-4 hours when inoculated in doses of 4-8 c.c. 



The toxin appears to be produced in only minimal quantity in cultures. 

 MacFadyen by triturating the bacilli in liquid air (p. 379) obtained a toxin 

 which killed rabbits when inoculated intra-venously in doses of 1 c.c. 



5. Agglutination. The serum of persons suffering from " food-poisoning " 

 due to the aertrycke bacillus agglutinates that bacillus but has little action 

 on the gaertner bacillus. 



The serum of animals immunized with the aertrycke bacillus agglu- 

 tinates the homologous bacillus and contains co-agglutinins in considerable 

 amount for the paratyphoid B bacillus, but has little or no action on the 

 gaertner bacillus. 



By means of the agglutination reaction with the serum of immunized 

 animals the aertrycke bacillus is therefore at once distinguished from the 

 gaertner bacillus, but by a simple determination of the limits of agglutination 

 it is generally impossible to differentiate it from the paratyphoid B bacillus, 

 both organisms being agglutinated by the respective specific serums in about 

 the same titre (p. 435). To distinguish between the aertrycke and the para- 

 typhoid B bacilli it is consequently necessary to adopt the method of 

 absorption of agglutinins (p. 436) (Boycott, Bainbridge). 



6. Absorption tests. If the agglutination titre of an antiaertrycke serum 

 be determined both for its own organism and also for the paratyphoid B 

 bacillus the two determinations will in most cases be found to be approximately 

 the same. On absorbing such a serum with its homologous bacillus all the 

 homologous agglutinins as well as the heterologous co-agglutinins will be 

 removed. 'But if absorbed with its heterologous bacillus the heterologous 

 co-agglutinins will be almost entirely removed while the serum will still 

 retain its power of agglutinating the homologous bacillus in high dilution ; 

 differentiation is thus rendered possible. The following table taken from 

 Bainbridge (Jr. Path, and Bact. xiii. p. 453) will ftiake these points clear. 



7. Complement fixation. By using an homologous bacillary extract and a 

 suitable dilution of- an antiserum the aertrycke bacillus can be clearly dif- 

 ferentiated from the paratyphoid B bacillus (Dean) (p. 437). 



SECTION IV. ISOLATION AND IDENTIFICATION OF THE 

 AERTRYCKE BACILLUS. 



In cases of food-poisoning the organism should be looked for in the suspected 

 meat, in the blood of the patient and in the stools ; and should a case prove 

 fatal, in the spleen and intestinal contents. 



