68 IMMUNITY 



process may be 600 c.c. of a virulent culture. Four weeks after the 

 last dose is given the serum is withdrawn. It is thought by Mar- 

 morek that the action of the serum is anti-bacterial, rather than anti- 

 toxic. It has been found that the use of streptococci from human 

 sources is the most efficient for the immunization of horses. 



Anti-streptococcus serum is of some value in infection and 

 diseases caused by streptococci. Of these it has been used in puer- 

 peral fever, erysipelas, and septicaemia. It has by no means won an 

 undisputed place, like diphtheria anti-toxin. 



The Anti-pneumococcus serum is prepared in the same way. 

 Horses are immunized by the injection of living cultures, and the 

 horse's blood, after a period of treatment by cultures, is drawn off, 

 preserved with tri-cresol and used in a manner similar to diphtheria 

 anti-toxin. Its use has not been attended with any marked results. 

 It is a curious phenomenon that pneumococci grow better in the 

 serum of a horse immunized against pneumococci than in noimal 

 horse serum. Autolysates of virulent pneumococci are now used 

 for immunizing animals. These seem to raise the anti-bodies 

 better than whole cocci. 



There are anti-toxic sera for use against Botulism, or meat pois- 

 oning, pyocyaneus infection, hay-fever, staphylococcus infec- 

 tion, Malta fever, and typhoid, that have been used without much 

 success. They have a certain scientific interest, but are of no great 

 clinical value. 



Anti-plague Serum. Yersin, a French bacteriologist, treated 

 horses with living cultures of plague bacilli, and after a long period 

 of immunization used a serum which either effectually vaccinated an 

 individual against the plague, or greatly modified the disease after it 

 had once begun. Later it was found that heat killed cultures were 

 just as effectual. 



In 142 cases of plague treated with serum, 24 died, a mortality 

 of 14.78 percent, while in 72 cases untreated, 46 died, a mortality 

 rate of 63.72 percent. 



The action of the serum is bactericidal, as well as anti-toxic. The 



