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 sufticiently 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 
