PROPHYLACTIC IMMUNIZATION OR VACCINATION 627 



more than four successive transfers from a human case of vaccinia, 

 and is guaranteed to give 100 per cent, of " takes" in primary vaccina- 

 tion. 



Animals. Various animals have been used, but female calves from 

 two to four months of age are preferable. Older animals may be used, 

 and in several European institutes cows are usually employed. With 

 properly constructed operating-tables, they may be handled with 

 comparative ease. Rabbits have also been used, especially in pro- 

 pagating the seed virus and to obtain pure and highly active viruses. 



The calves are kept under supervision for at least a few days. In 

 some institutes they are tested with tuberculin, although with good 

 veterinary inspection this test is not necessary. Soon after admission 

 the animal is clipped and given a thorough cleansing, which includes the 

 feet and the tail. 



On the day before vaccination is to be performed the belly-wall is 

 cleanly shaved from the cuneiform cartilage to the pubis, and well up 

 on the inner sides of the thighs and the flanks. The skin is then 

 thoroughly washed. Just preceding the vaccination the animal is 

 fastened to the operating-table and the abdomen and inner surface of 

 the thighs prepared as for an aseptic abdominal section, i. e., a thorough 

 scrubbing with hot water, green soap, and soft brush, followed by alcohol 

 and sterilized water, the parts being then dried with a sterile towel. 

 All other parts are covered with sterile sheets, and the calf is now vac- 

 cinated under aseptic precautions. 



Vaccination. About 100 small scarifications are now made in these 

 areas, preferably by cross-scratches or in rows of lines about one to 

 two centimeters square and at least one to two centimeters apart. 

 The scarification is simple, but usually brings a small amount of blood. 

 After they have been made, they are mopped with sterile gauze and 

 rubbed with the charged slips, using one or two slips for each small area, 

 depending on the amount of virus each slip contains. The lesions are 

 allowed to dry, and are then covered with sterile gauze or a simple 

 protective paste, or are left entirely uncovered. 



Precautions should be taken to keep the animals as clean as possible. 

 Inoculated animals are to be kept in stalls or stables apart from those 

 under observation. The stable should be so constructed that the floors 

 can be flushed daily with a hose and hot water. Excreta should be re- 

 moved promptly. No bedding is permissible, and means should be 

 provided for fastening the legs and preventing the animal from kicking 

 the scarifications. 



