vin AGGLUTINATION OF B. PESTIS 205 



animals that had previously been prepared and protected 

 by injection of non-fatal doses of plague culture or by 

 injection of Haffkine's prophylactic. Thus Leumann, in 

 various reports from the Bombay Plague Laboratory, 

 mentions such positive agglutination results ; Zabolotny 1 

 likewise describes such positive results ; Dr. Markl 2 and 

 others have stated the same. But there is no unanimity 

 of these observers, either as to the degree of dilution or as 

 to the time in which the addition of the blood serum 

 produced the agglutination ; there is in most of their 

 descriptions merely the statement that positive results 

 were obtained. Further, there is no detailed account of 

 the manner in which the test was applied. As I have 

 pointed out in the Lancet (February 16, 1901), it is 

 extremely difficult to obtain an emulsion of plague culture 

 suitable for the agglutination test, owing to the fact that 

 the B. pestis has in all media a tendency to grow in 

 coherent masses, the individual bacilli becoming naturally 

 agglutinated by an interstitial (intercellular) sticky sub- 

 stance. As is well known, and as I have pointed out in 

 my report for 1896, the B. pestis forms in broth cultures 

 granules and. flocculi of agglutinated masses, which, even 

 on shaking, do not readily or to any large extent break 

 up into their constituent elements. Wherefore a broth 

 culture cannot be used for the test since the plague bacilli 

 are already showing agglutinated masses. The same is 

 the case with agar cultures. As is known, and as has been 

 repeatedly pointed out (I.e. 1896), the B. pestis grows on the 

 surface of agar as a characteristic filmy translucent sticky 

 layer ; so that when, with a platinum needle, a particle is 



1 Archives des Sciences Biologiques de St. Peter sbourg, vol. viii. ET. 1. 

 2 Centralbl. fur Bakteriologie, etc., vol. xxix. No. 21, p. 810. 



