268 ORIENTAL PLAGUE chap. 



dose of culture of dead plague bacilli or their extracts. 

 Thus HafFkine uses a broth culture containing a large 

 amount of bacillary growth, which culture has previously 

 been subjected to heat (70° C.) sufficient to kill the bacilli. 

 As Haffkine has shown, and as is generally the practice 

 wherever this prophylactic is used, the amount of bacillary 

 growth determines in a somewhat rough-and-ready manner 

 the efficacy and therefore the dosage of the prophylactic. 

 With Calmette, as also at the Pasteur Institute, the 

 prophylactic is a sterilised emulsion of the bacillary 

 growth taken from the surface of solid agar cultures. 

 The German Plague Commission also recommended an 

 emulsion of agar culture sterilised at 65° C. On the 

 other hand, Lustig uses in preparation of his prophylactic, 

 or rather his curative serum, the precipitate obtained 

 from an alkaline emulsion of an agar culture of B. pestis. 

 Similar processes are employed by others in preparation 

 of their plague prophylactic. According to numerous 

 results hitherto published in India, South Africa, and 

 elsewhere, the first two prophylactics, viz. Haffkine's 

 and prophylactic prepared in the manner adopted by 

 Calmette and the Pasteur Institute, are those which are 

 most reliable. Such disadvantages as are attached to 

 them are the disadvantages generally inherent to all 

 fluids prepared from artificial cultures, viz. the difficulty 

 of preservation, and, above all, the difficulty of securing, 

 when large amounts of material are prepared at one 

 time, uniformity of strength, i.e. efficacy for every single 

 dose. 



The above disadvantages have led me to investigate 

 the matter in a new direction — to attempt, that is, to 

 obtain a prophylactic free from the above defects. The 





