.MODE OF SPREAD OF INFECTIVE DISEASES. 757 



favourable ; but here also we cannot yet come to a final 

 judgment on account of our ignorance of the length of 

 duration of the protection, the absence of a calculation 

 as to the cost, and the neglect up to the present time 

 of other prophylactic measures in the infected districts. 



The inoculations for anthrax have excited special in anthrax, 

 interest. They were carried out in the first place with 

 bacilli attenuated by Toussaint's method (p. 657); a 

 practically useful vaccine was later produced by Pasteur 

 and Chauveau, each by a different method. Pasteur Pasteur's 

 employed as his first vaccine a cultivation in meat m 

 infusion which had been kept at a temperature of 42 

 to 43 C. till it no longer killed guinea-pigs and rabbits, 

 but was still fatal to mice (see page 657). One 

 division of a Pravaz syringe of this vaccine is injected on 

 the inner side of the hind thigh of sheep ; in the case of 

 cattle two divisions are injected behind the shoulder. 

 After the lapse of twelve to fourteen days a similar in- 

 jection is made with the second vaccine, which has been 

 kept at 42 to 43 C. till rabbits are not killed by it, 

 while mice and guinea-pigs still die. It was not till 

 Koch introduced the method of testing the cultivations 

 on these three kinds of animals that it was possible to 

 know exactly the degree of virulence of the organisms. 

 Chauveau makes his vaccine by heating the organisms 

 for a shorter time at higher temperatures ; he em- m 

 ploys fresh anthracic blood and not cultivations, and in 

 order that it may be warmed as quickly as possible, he 

 collects it in very small glass tubes. More recently 

 Chauveau, in conjunction with "Wosnessenksi, has also 

 utilised for the purpose of attenuation the simultaneous 

 action of high pressure (page 660). The virulence of 

 his vaccine lies somewhat between that of the two vaccine 

 materials employed by Pasteur ; it is chiefly intended for 

 cattle, and they are inoculated in the ear by means of a 

 syringe. The other methods of attenuation and protec- 

 tive inoculation for anthrax have not as yet been intro- 

 duced into practice. 



In judging of the results obtained we must, in the 

 first place, note that the effect of the protective inocu- 



