292 SUMMARY OF CURRENT RESEARCHES RELATING TO 



a survival percentage of '■'>■>. When, however, the avirulent organisms 

 were grown in a medium containing serum broth, a high degree of prol 

 tion (73 p.c.) was afforded against the same besi dose, even although 

 the protecting dose was reduced to .-, 1 ,,- of the original dose. 



When rats vaccinated against these organisms of enhanced virulenc 

 were tested against a culture of moderate virulence, which was obtained 

 Prom one of Castellani's Ceylon cases, only 59 p.c. survived the tesl 

 inoculation. The degree of immunity conferred was not striking, as 

 50 p.c. of unprotected controls survived inoculation with the same test 

 dose of organisms. Thus the protection afforded by the Strong antigeE 

 against the Castellani strain was not nearly so good as that afforded 

 against the Laboratory strain, notwithstanding the fact that the latter 

 was the more virulent. Furthermore, of 41) rats vaccinated with the 

 Strong antigen, 36 p.c. survived the test inoculation with the Laboratory 

 strain, while of 47 rats vaccinated with the Laboratory strain antigen 

 and tested with the same strain, no less than 60 p.c. survived. It is 

 concluded that the two antigens are not identical, and that cross - 

 immunization is not complete. It is suggested that such differences in 

 antigenic properties may to some extent account for the disappointim: 

 results obtained in Java and elsewhere with Haffkines' prophvlactic 

 fluid. 



Development of Bacillus pestis in Bugs.* — A. W. Bacot has con- 

 firmed the observations of Yerbitsky and others as to the possibility of 

 the bug (Cimex lectularius) becoming a carrier of plague, under experi- 

 mental conditions. Bugs were allowed to suck the blood of infected 

 mice that were in the comatose condition that precedes death from 

 plague, and, if they managed to survive the infecting meal, they were 

 found to be capable of carrying Bacillus pestis, and of reinfecting mice 

 for a period of time up to forty-eight days. A certain proportion of the 

 bugs, however, and probably all newly hatched ones, do not survive the 

 ingestion of the bacilli, and die in a paralyzed condition. 



The structural character of the ingested blood is preserved unaltered 

 for many days in the crop of the insect, and the development of B. pestis 

 is slower, and the resulting growth looser, than is met with in the case of 

 flea infection. This, taken in connexion with the fact that there is not 

 any distinct valve between the pump and the crop, precludes the idea 

 of mechanical blockage, such as has been met with by Bacot and Martin 

 (see this Journal, 1914, p. 295) in fleas in which the proventriculus 

 becomes blocked with plague culture. 



One of the difficulties encountered in Bacot's experimental work was 

 due to the eating of the bugs by the mice in the cages. This undesir- 

 able state of affairs was overcome by placing pieces of wood, in which a 

 number of saw cuts had been made, in the cages. The bugs were thus 

 afforded cover from the attacks of their rodent hosts. 



Autogenous Living Vaccine in the Treatment of Enteric Fever.f 

 Major E. A. Bourke, Lieut. I. IX Evans, and Lieut. S. Rowland report 



* Journ. Hygiene, Plague Suppl. iv. (1915) pp. 777-92 (2 pis.), 

 t Joum. R. Med. Corps, xxiv. (1915) pp. 5-12. 



