VACCINATION. 739 



virus rubbed in with a spatula. Within from five 

 days to a week the vesicles are in such condition 

 that the lymph may be collected, the contents 

 either being squeezed out with suitably formed 

 forceps or scooped out with a sharp spoon. De- 

 pending on the area vaccinated, the lymph col- 

 lected from a single calf may be sufficient for 

 from 2,000 to 15,000 vaccinations in man. Be- 

 cause of the immunity which is conferred, calves 

 can be used but once for the production of vaccine 

 virus. 



All other methods of preserving lymph have 

 been largely abandoned for the process of 

 glycerinization, the glycerin being very inti- 

 mately mixed with the virus by mechanical 

 means and allowed to remain in this state in 

 a cool place for from six to eight weeks before 

 the product is put on the market. Dried vaccine 

 on ivory points is still used to some extent, the 

 points being coated directly from the vesicles. 

 Dried vaccine retains its power for from two to 

 four months or longer when kept in a cool, dark, 

 dry place. Glycerinated lymph has many advan- 

 tages, the most important of which relates to the 

 bactericidal action of the glycerin by which the inr Bacteria. 

 lymph is freed from the pathogenic bacteria (e. g., 

 staphylococci) which in former times caused ser- 

 ious complications in vaccination. The glycerin 

 is supposed to destroy such organisms to a large 

 degree without, however, injuring the vaccine 

 virus itself. It is also stated that glycerinated 

 lymph is much more durable than the dried; that 

 its potency may be retained for eight months or 

 longer under suitable conditions. Rosenau has 

 recently called attention to the fact that the bac- 



