324 PROTECTIVE INOCULATIONS. 



upon the results obtained. The quantities given at first were small, 

 but increased gradually until large amounts of the material used could 

 be injected without bad results. This treatment of the animals must 

 be carried out very carefully, and requires six to eight months' time 

 before the serum is sufficiently potent to be of any practical use. As 

 the treatment continues, the power of the serum to check the motility 

 of the hog-cholera germ increases with rapidity. The length of im- 

 munity produced by the injection of serum is short, and more perma- 

 nent immunity can apparently be secured by using in addition to 

 serum the products of the germs." 



The results of extensive inoculations (thirty-five thousand animals) 

 which have been made by the Agricultural Department during the past 

 two years have not yet been published, but it is understood that as a 

 rule these results have been quite satisfactory. 



HOG ERYSIPELAS. 



Pasteur's first studies relating to the etiology of "rouget" were 

 made, in collaboration with Chamberland, Roux, and Thuillier, in 

 1882. Pasteur found that the virulence of his cultures was increased 

 by passing them through pigeons and diminished by passing them 

 through rabbits. By a series of inoculations in rabbits he obtained 

 an attenuated virus suitable for protective inoculations in swine. In 

 practice he recommended the use of a mild virus first, and after an 

 interval of twelve days of a stronger virus. These inoculations have 

 been extensively practised in France, and the fact that immunity may 

 be established in this way is well demonstrated. There has been some 

 doubt, however, as to the practical value of the method, as its appli- 

 cation has been attended with some loss, and there appears to be 

 danger that the disease may be spread by the alvine discharges of 

 inoculated animals. In a region where the annual losses from the 

 disease are considerable, and where the soil is, perhaps, thoroughly 

 infected with the bacilli, protective inoculations probably afford the 

 best security against loss. But when it is practicable to stamp out 

 the disease by quarantine of infected animals, disinfection of localities 

 in which cases have occurred, and strict attention to cleanliness, this 

 will probably be found the best method of combating the malady. 



Chamberland (1894) states that in the preceding seven years, dur- 

 ing which time protective inoculations were practised in France on a 

 large scale, the mortality from rouget has been reduced to 1.45 per 

 cent, whereas before these inoculations were practised the mortality 

 from this disease was about twenty per cent. Losses amounting in 



