386 DISEASES OF SWINE 



amount of a solution of carbolic acid is added for the purpose of 

 keeping it from spoiling until ready for use. The amount added 

 is about the same as that used for keeping the serum; that is, to 

 each 9 ounces of the virulent blood one ounce of a 5 per cent, 

 solution of carbolic acid is added. This small amount of carbolic 

 acid is sufficient to enable one to keep this virus blood for several 

 days if handled properly, and still is not enough to do any harm 

 to the animal into whose body it is injected. 



Virus is put up in smaller bottles than the serum and is properly 

 labeled to avoid any mistake. Otherwise, in general appearance 

 it is very similar to serum, being perhaps a little lighter in color 

 as a rule. 



Virus blood, unlike serum, will not hold its strength for an 

 indefinite period. We have found that serum can be kept for 

 almost any reasonable length of time, and still prove to have the 

 power of protecting the animals into which it may be injected 

 against an attack of cholera. Virus blood, on the other hand, 

 must be used very soon after it is drawn from the sick animal if 

 we are to obtain the best results from its use. The sooner it can 

 be used the better, and under no conditions should it be used 

 after it is more than fifteen days old. When putting up virus 

 blood, manufacturers label the bottles not to be used after a cer- 

 tain date. This is the date after which it becomes unsafe to make 

 use of the virus, and, if it has not been used at this date, it should 

 be destroyed by burning or other safe method. 



Method of Injection. — In giving the double method of treat- 

 ment to a herd the work is done in just the same manner as for 

 the single method, with the exception that a dose of the virus is 

 also injected at the same time the serum is given. 



The animals are caught and securely held, as in the case of the 

 single treatment. All the instruments are carefully cleaned and 

 boiled, and for this method we also prepare the small syringe pre- 

 viously mentioned, which is intended for use in giving the virus. 

 The animal is scrubbed with the disinfectant solution, and the 

 skin in the region where the needle is to be inserted painted with 

 tincture of iodin. The large syringe is filled with serum, the weight 

 estimated, and the temperature having been already taken the 

 proper dose of serum for the weight of the animal is now injected 



