MANUFACTURE OF HOG-CHOLERA SERUM 351 



easier than the intravenous system, and requires little or no skill 

 to introduce the virus in this manner. The slow method has 

 another advantage, in that it can be used where the manufacturer 

 has not enough virus on hand at one time to complete the hyper- 

 immunization. This condition may arise at a small serum plant, 

 seldom if ever at large plants. 



Some men seem to have a little bad luck with the intravenous 

 injection, and report the loss of large numbers of animals following 

 this means of hyperimmunization. Those who have used the 

 method most extensively, however, do not report such results 

 with any degree of frequency, and it is rapidly gaining in favor 

 even with those that at first were unsuccessful in its use. 



There are a number of serious objections to the use of the sub- 

 cutaneous method. One of these is the question of absorption. 

 This is the all-important point in hyperimmunization. It is not 

 so much the amount of virus that we place in the body of the ani- 

 mal as it is the amount absorbed that counts in producing a good 

 serum. The more virus we can get into the body and get absorbed 

 without killing the hog, the better will be the quahty of the serum 

 resulting. 



Dr. Connaway, of Missouri, is of the opinion that the subcuta- 

 neous injection of virus has an advantage, in that it leads to ab- 

 sorption through the lymphatics and brings the virus quickly in 

 contact with those cells that are later to produce the antibodies. 

 This may be true, but the fact remains that after subcutaneous 

 injections there is often a large amount of the virus that remains 

 at the local point of injection and is not taken up at all. Abscesses 

 often form in the region of the injection, and this cannot have 

 other than a bad effect upon the quality of the serum. An animal 

 with several large abscesses over the body cannot have clean 

 blood and cannot produce clean serum. Some of the toxic ma- 

 terial, and often large numbers of the pus-producing germs, are 

 taken into the blood and pass out with it into the serum. 



Dr. Niles, of the Ames serum plant, reporting the results of 

 his early experiments with the subcutaneous method, states that 

 the serum so produced was unreliable. One batch might be good, 

 while another might be almost worthless. Dr. Williams, of the 

 Minnesota State Experiment Station, also reports a large amount 



