THE MANUFACTURE OF VACCINES. 471 



the stock virus. The animal under treatment is placed on a special 

 operating table, the ventral surface of the body is shaved and cleansed 

 and with a sterile instrument (curette) the skin is scarified in parallel 

 straight lines over the greater portion of the abdomen. By means of a 

 sterile instrument, the stock virus or "seed" is inoculated in the scarified 

 areas. The animal is then released and placed in the propagating room. 

 During the process of propagation of the vaccine all possible precaution- 

 ary measures should be used to avoid the introduction of contaminating 

 bacteria. It is important that an attendant be constantly present, day 

 and night, whose duty it is to remove instantly all dirt and feces and keep 

 the room as clean and free from microbial contamination as possible. 



At the expiration of from five to seven days, numerous characteristic 

 vesicles will have developed on the inoculated areas of the skin of the 

 animal. These are filled with a thick, sticky exudate. At this time the 

 animal is removed to the operating table, the field of operation is washed 

 with sterile water and the contents of the vesicles are removed with a 

 sterile curette. According to regulations of the Federal Government 

 all animals used in this work must be slaughtered before the vaccine 

 is removed and then submitted to careful autopsy. After removing the 

 cow-pox exudate, or vaccine, it is handled under aseptic precautions and 

 mixed with about 50 per cent glycerin, which serves as a preservative. 

 Small portions of the material are then inoculated into guinea-pigs for 

 safety tests and the product is placed in the refrigerator. Under the 

 combined influence of the glycerin and low temperature extraneous 

 microbial contamination gradually disappears. Potency tests of the 

 vaccine are conducted by the cutaneous application of the vaccine on 

 calves, rabbits or on the slightly scarified, scrotal surfaces of guinea-pigs. 

 In addition to the safety and potency tests, inoculations are made into 

 culture media which are placed under both aerobic and anaerobic con- 

 ditions to insure the absence of harmful bacteria. For the detection 

 of the presence of B. tetani the product is submitted to a special test by 

 transferring i c.c. into a quantity of glucose beef bouillon or other special 

 culture media, placing the culture under anaerobic conditions and incu- 

 bating at body-temperature for about ten days. After the incubation 

 any resulting growth is removed by filtration and the filtrate is injected 

 into guinea-pigs. The absence of symptoms in the treated animals shows 

 that no tetanus toxin has been elaborated in the culture and therefore the 

 vaccine does not contain the spores of B. tetani. 



