84 VACCINE AND SERUM THERAPY. 



process of active immunization by means of living organisms at- 

 tenuated by passage through cows. 



The methods of obtaining virus for vaccination vary. Up to 

 1870, virus was usually obtained from the pustule of the vacci- 

 nated individual. Now, however, vaccine is usually obtained from 

 young calves which have been inoculated on the abdomen and 

 thighs with vaccine from the pustules of healthy children or calves. 

 The pustules on inoculated calves are cleaned and opened on about 

 the third or fourth day and from the material contained in them 

 either so-called "vaccine points" or "glycerinated virus" is made. 

 The animals from which the vaccine is obtained are kept as clean 

 as possible, asepsis and anti-sepsis being employed as much as is 

 possible. When all precautions are taken the vaccine still con- 

 tains many organisms. 



Vaccine points are made by dipping sterile bone slips into the 

 material from the pustule. The vaccine is then dried, kept under 

 aseptic conditions and is ready for use. Glycerinated virus is made 

 by softening the pustular material with glycerine. Glycerine has 

 the additional advantage of killing many bacteria in the virus and 

 makes it possible to put the virus up in tubes. Small-pox vaccine 

 is seldom entirely sterile, the organisms present, however, in a well- 

 prepared vaccine, consist of only few species and are usually harm- 

 less. After two to three weeks action of glycerine, vaccine is 

 frequently free from bacteria. 



The durability of potency and efficiency of small-pox vaccine 

 varies. Some vaccines lose their value in one month while others 

 will remain efficient for three to four months. This emphasizes 

 the importance of using fresh virus for vaccination against small- 

 pox. 



The method of vaccination varies. It is the custom now to 

 produce scarifications of one-eighth to one-fourth of an inch in 

 diameter on the well-cleaned arm or thigh. When vaccination is 

 made on the arm, the area selected is about the point of insertion 

 of the deltoid muscle. In cleaning the part where vaccination is 

 to be made it is to be remembered that all antiseptics must be re- 

 moved with sterile water before inoculation is made. Scarifica- 

 tion is only made severe enough to produce an exudation of serum, 

 bleeding being avoided as much as possible. After scarification, 



