SUMMARY OF SERUM MANUFACTURE 365 



treatment is prepared in a slightly different manner from that 

 intended for immediate use at the serum plant. This virus that is 

 to be sent to the field is defibrinated the same as that to be used at 

 the home plant, and there is then added to it 1 e.c. of 5 per cent, 

 carbolic acid solution for each 9 c.c. of virus blood. In this way 

 its keeping qualities are improved and it is prevented from early 

 deterioration. This virus is then placed in glass-stoppered, dark- 

 colored bottles and kept in a cool place until ready for use. 



Virus Also to Be Tested. — Check tests should also be made on 

 all virus used for hyperimmunization purposes at the serum plant. 

 If the virus blood given at this time is of poor quaUty it will not 

 produce the desired reaction on the part of the tissue cells of the 

 animal into which it is injected. Failure to get this reaction would 

 mean a poor quality of serum. For this reason it is advisable to 

 test out the virus used at each hyperimmunization, in order to 

 make certain that a virus has been injected that has sufficient 

 disease-producing power to ensure a strong reaction on the part 

 of the tissues and an accordingly large formation of germ anti- 

 bodies. 



By using a little tact these tests can be so arranged that the 

 one series of tests serve to check the virus used for hyperimmuniza- 

 tion and the serum intended for shipment to the field. 



How Long May Serum Be Kept? — This is a question that some- 

 times arises. In case a large amount of serum is made during the 

 winter months it is of interest to know if this product may safely 

 be held over until the following summer and fall, and then used in 

 the field. Most tests to date show very conclusively that this can 

 be done with perfect safety. In fact, Dr. Niles, of the United 

 States Serum Plant at Ames, Iowa, has shown that serum can be 

 kept as long as a year and over without losing its strength. 



The most important factor in the keeping of serum for several 

 months in this manner before use is to keep it cold during all this 

 time. If the serum is kept cold there is little or no danger of it 

 deteriorating. It is a good plan, however, both at the time that 

 the serum is made and at the time that it is about to be sent into 

 the field, to have germ tests made by means of plate-cultures. This 

 should be done by an experienced bacteriologist, and the presence 

 of any large amount of germs would prohibit the use of the serum 



