418 DISEASES OF SWINE 



ready affected ; this being shown by the presence of a high tempera- 

 ture. In those animals which do not show any fever, and in 

 which we are accordingly safe to conclude the disease has not yet 

 made itself manifest, the double method should be used, injecting 

 the serum and virus. By this means we insure the development 

 of a permanent immunity in every animal in the herd. 



This case also gives some idea as to what may be expected in 

 those cases where serum is used after the outbreak has already made 

 a start. In this herd 82 per cent., or over 375, of the animals had 

 a high temperature. Some of these temperatures ran even as high 

 as 108° F. or higher. Yet out of this large number of sick animals 

 only 6 were lost after the injection of the serum had been made 

 the second time. 



This is a more briUiant result than can be hoped for in the 

 majority of cases. Dr. Sihlerwas perhaps aided some in this case 

 by the fact that these animals had several weeks before received a 

 dose of serum, and even though this first serum may have been of 

 poor quality, yet it probably had left some effects which would in 

 part account for the brilliant results that followed this second 

 treatment. 



(16) The best rule to follow in giving the serum treatment 

 is to give the single method wherever the disease is already 

 present, as shown by the presence of temperature or other signs 

 of cholera. 



Some men prefer to give the single method in every animal of an 

 infected herd, whether they show a temperature or not. This 

 practice is based on the fact that the animals, by being in an in- 

 fected feed lot and in close contact with animals which have the 

 disease, will take enough of the virus with the air they breathe and 

 the food they eat to produce the same results as would follow the 

 giving of the virus by means of injection of virulent blood. 



This cannot be absolutely depended upon, and in order to 

 make sure that every animal in the herd will be left with a perma- 

 nent immunity if they survive it is necessary that the entrance of 

 virus into the body be made certain by its injection. 



Remember, the immunity produced by the injection of the serum 

 alone in those animals which are susceptible to cholera will be only 

 temporary in character. 



