﻿II. DISCUSSION OF THE PROPHYLACTICS PREVIOUSLY 



EMPLOYED. 



Before proceeding directly to this discussion of the experimental work, 

 it will be advantageous to mention the various prophylactics which have 

 already been used in human beings, and briefly to review the methods 

 of preparing them and the immunizing powers which they possess. 



1. METHODS OF PREPARATION. 



Haffkine's 7 prophylactic against plague consists of the killed bouillon cultures 

 of the pest bacillus. The organism is grown in 3-liter flasks of bouillon upon 

 the surface of which clarified butter or coconut oil is distributed. The cultures 

 are kept for six weeks at a temperature between 25° and 30° C. The bacteria 

 form stalactite-like growths, which extend from beneath the surface of the oil 

 downwards. The flasks are shaken every few days, when the organisms fall to the 

 bottom of the vessel and a new growth takes place above. After five or six 

 weeks' growth, in order to be sure that the bouillon cultures are pure, subcultures 

 are made from them upon agar slants. The bouillon cultures are then killed by 

 heating for one hour at 65° to 70° C. and, after their sterility is proven, sufficient 

 carbolic acid is added to form a 0.5 per cent solution. The prophylactic is 

 placed in 30 cubic centimeter bottles and it must be shaken before use, since 

 the killed bacteria naturally settle to the bottom of the vessel. The dose for 

 men is from 3 to 3.5 cubic centimeters, for women from 2 to 2.5 cubic centimeters 

 and for children from 0.5 to 1 cubic centimeter. Recently, Haffkine has in 

 special cases recommended as high as 20 cubic centimeters for a single injection. 

 He also frequently advises a second and even a third inoculation. 



Another form of prophylactic against plague is that which was recommended 

 by the German Plague Commission 8 (Gaffky, Pfeiffer, Sticker and Dieudonne) 

 and which consists of the killed agar cultures of the virulent pest bacillus. 

 Forty-eight hour agar slants of the organism are suspended in saline solution 

 or bouillon and killed by heating for one hour at 65° C. Carbolic acid is then 

 added to 0.5 per cent. The dose for a grown man is one agar culture. This 

 prophylactic has many advantages over that recommended by Haffkine since 

 with it an accurate dose as well a fixed virulence for the organism employed 

 can be obtained. Moreover, it is much less dangerous, since either the tetanus 

 bacillus or the organism of malignant oedema may develop in the bouillon cultures. 

 Such anaerobic organisms will naturally not multiply on the agar slants. 



Haffkine claimed as an advantage of his method that certain metabolic sub- 

 stances of the plague bacillus were contained in the fluid media which rendered the 

 prophylactic more effective. 



7 Brit. Med. Journ. (1897), 1461; also Lancet (1899), 77, 1095. 



8 Berieht. der deutsch. Pest Kommission. Arb. a. d. 7c. Gsndhtsamte, Berl. 

 (1899), 16, 306. 



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