424 THE QUESTION OF IMMUNITY AND ANTITOXINS 



Anti-Typhoid Inoculation.— It is now known that the serum 

 of persons who have recovered from typhoid fever, and the serum 

 of animals artificially immunised against virulent typhoid bacilli, 

 protect against the typhoid bacillus. Animals have now been 

 immunised by injections of the toxins of the typhoid bacillus ; and 

 their serum aids in the destruction of the bacilli which produce the 

 toxins. Acting on these principles, Wright has prepared a vaccine 

 against typhoid fever. A virulent twenty-four hours culture is 

 emulsified in bouillon, and killed by heating for five minutes at 60° 

 C. For use, one-twentieth to one-fourth of the dead culture is 

 injected hypodermically, usually in the flank.* The effect of the 

 inoculation is some local tenderness and swelling with enlargement 

 of adjacent lymph glands. Within ten days the blood of the 

 inoculated person begins to show a positive Widal reaction, owing 

 to its immunising properties, and it is also bactericidal in vitro. 



Haflkine's Ppeventive Inoculation for Plag-ue.— In plague 

 the same plan has been followed. Luxurious crops of Kitasato's 

 plague bacillus are grown on ordinary broth with the addition to 

 the surface of a film of oil or fat ("ghee"). Under the globules of 

 fat flakes of plague culture grow like stalactites, hanging down into 

 the clear broth. The culture is kept at 25° C. These are, every few 

 days, shaken to the bottom, and a second crop grows on the under- 

 surface of the fat. In the course of six weeks a number of such 

 crops are obtained and shaken down into the fluid, until the latter 

 assumes an opaque milky appearance. The purity of this culture 

 is controlled by transferring with a sterile pipette a small quantity 

 to a dry agar tube, and noting the appearance of the growth by 

 reflected light through the thickness of the agar. The culture is 

 now, unlike the cholera vaccine, exposed to a temperature of 65° C. 

 for one hour in a water-bath, and a small quantity of carbolic acid is 

 added ('5 per cent.), by which processes the bacilli are killed. The 

 dose is 5 to 10 c.c. This preparation has the advantage of being 

 easily prepared, obtainable in large quantities, and requires no animals 

 in its preparation. When inoculated, it produces local pain and 

 swelling at the site of inoculation, and general reactive symptoms such 

 as fever. From a careful analysis of the results of this inoculation, it 

 is shown that the ef&cacy of the prophylactic depends upon the 

 virulence of the bacillus culture from which the vaccine is prepared, 

 and upon its dose and ability to produce a well-marked febrile 

 reaction. It appears to be more effective in the prevention of deaths 

 than of attacks. f 



* For methods employed in preparation of the vaccine, see Brit. Med. Jour,, 

 1900, vol. i., p. 122 (Wright). 



t Proc. Boy. Soc, 1900 ; Report of Medical Officer to Local Oovernment Board, 

 1902, pp. 357-94. 



