THE PARATYPHOID B. BACILLUS 435 



3. Vaccination. Properties of immune serums. 



Animals can be easily immunized by inoculating them with heated or 

 attenuated cultures (vide infra). Franchetti has prepared an agglu- 

 tinating and antitoxic serum by inoculating rabbits with his toxin (vide 

 supra). 



Boycott found that vaccination with the paratyphoid B. bacillus was 

 protective against the paratyphoid B. bacillus but not against the aertrycke 

 bacillus. 



4. Agglutination. 



Agglutinins are developed in the blood in response to a naturally acquired 

 infection in man and to the inoculation of the bacillus in animals. 



Serum reactions in human paratyphoid B. fever. It would appear that a 

 careful determination of the ultimate limits of agglutination will, at any 

 rate in the great majority of cases, give accurate information as to the nature 

 of a typhoid or paratyphoid [B.] serum (Boycott). 



As a rule a paratyphoid B. serum has little agglutinating action on the 

 typhoid bacillus : thus in a case recorded by Sacquepee and Rieux a para- 

 typhoid B serum agglutinated the paratyphoid B bacillus isolated from the 

 patient in a dilution of 1-2000 and the typhoid bacillus in only 1-40. 



But anomalous results are occasionally observed. Zupnik has shown that 

 the serum from cases of enteric fever determined by isolation of the typhoid 

 bacillus may agglutinate the paratyphoid B. bacillus in as high or even in 

 an higher dilution than it agglutinates the homologous organism. Pratt 

 found that the serum of a patient from whose blood he isolated the typhoid 

 bacillus agglutinated the paratyphoid B. bacillus in a dilution of 1 in 200 and 

 had no action on the typhoid bacillus in a dilution of 1 in 10. 



Normal human serum may agglutinate the paratyphoid B. bacillus up to 

 a dilution of 1 in 100. But in paratyphoid B. fever the serum reaction is 

 usually manifested in relatively high dilutions up to 1-1000 ; and extra- 

 ordinarily active human serums have been encountered by Savage (1-70,000) 

 and Zupnik (1-140,000). Boycott's three cases all agglutinated in a dilu- 

 tion of 1-5000, and in only one of 21 cases observed by Zupnik was the 

 reaction less than 1-1000. 



Paratyphoid B fever cannot be diagnosed on a demonstration that the 

 serum of a person suffering from an illness resembling enteric fever fails to 

 agglutinate the typhoid bacillus even in low dilutions. And still less is a 

 diagnosis of paratyphoid fever justified by the bare fact that agglutination 

 is observed with a paratyphoid B or similar bacillus (Boycott). Forty-one 

 per cent, of typhoid serums (in a consecutive series of 86) agglutinated the 

 paratyphoid B bacillus (Boycott). 



In the paratyphoid B food-poisoning epidemic investigated by Bainbridge 

 and Dudfield the serum of the persons involved agglutinated the para- 

 typhoid B bacillus in dilutions of 1-100 to 1-400. 



Animal serums. The serum of animals inoculated with the paratyphoid B 

 bacillus acquires the property of agglutinating the bacillus in high dilution. 

 At the same time co-agglutinins are developed, especially for the aertrycke 

 bacillus ; indeed the amount of co-agglutinin for this organism may be so 

 considerable as to be almost equal in amount to the specific agglutinin. 



Bainbridge finds that if immunization be effected with living bacilli, instead 

 of with sterilized cultures, the amount of co-agglutinin is much less and the 

 titre of the specific agglutinin higher. 



In the case of the paratyphoid B bacillus, which is relatively an highly 



