346 DISEASES OF SWINE 



importance not only at the time of injection, but also is essential 

 for comparative purposes later on when bleeding is commenced. 

 Every animal should show a gain in weight during the week or ten 

 days that elapse between date of hyperimmunization and the mak- 

 ing of the first tail bleeding. 



Methods of Injection. — The weight having been taken, and the 

 animal securely fastened in position, we are now ready to proceed 

 with the operation of hyperimmunizing. There are several ways 

 of injecting the virus blood into the body of the immune hog, the 

 more important being : 



(1) By intravenous injection. 



(2) By subcutaneous injection. 



(3) By intraperitoneal injection. 



Of these three methods, the one most used in this country is the 

 intravenous. Each of the other methods have some advocates, 

 but, in the main, their principal advantage is the fact that they are 

 easier than the intravenous. In every other respect they are less 

 desirable, and the serum obtained by use of either subcutaneous 

 or intraperitoneal injection is not of as reliable a character as that 

 secured when the intravenous method is used. Intravenous in- 

 jection has the one objection that it is somewhat more difficult to 

 give, especially in the hands of the beginner. The vein is often 

 hard to locate, and even after months of work operators frequently 

 have trouble in introducing the needle into the vein and securing 

 injection of the large amount of virus blood necessary for this 

 purpose. 



Point of Injection.- — In giving the intravenous injection prac- 

 tically all operators make use of the large veins on the upper surface 

 of the ear. These veins are comparatively large and can be con- 

 veniently reached. As soon as the hog has been secured in the crate 

 and the weight taken, the operator examines each ear, and selects 

 the one which seems to offer the more suitable vein. This ear is 

 then carefully washed with soap and water and one of the disinfect- 

 ant solutions, liquor cresoHs compound being the most commonly 

 used. This is followed by shaving of the hair from the ear and a 

 wash with alcohol, after which the ear is allowed to dry by evapo- 

 ration of the alcohol. It is now ready for the injection. 



The virus, obtained and prepared as described in a preceding 



