VACCINE-THERAPY 89 



In therapeutics serums may be used alone or in conjunc- 

 tion with vaccines — in fact, in many cases the combination 

 is a happy one, particularly in the diseases attributed to 

 the streptococcus. Again, in some diseases we are com- 

 pelled to fall back upon serums alone, as there are certain 

 specific infections where the causative bacterium has never 

 been isolated : hence vaccines — at least, according to the 

 present-day meaning of the word " vaccine " — are not pro- 

 curable. These specific diseases belong to what are known 

 as the ultravisible virus group, of which the following are 

 the principal : 



Swine fever. 



Canine distemper (probably). 



Rabies. 



Foot and mouth disease. 



Specific pleuro-pneumonia (Bovine). 



Rinderpest. 



Variolas. 



Cape horse sickness. 



It may be advisable to point out here there is a distinct 

 phenomena particularly recognized in human medicine 

 following upon the injection of sera under certain cir- 

 cumstances, and it is known as " serum disease." In 

 animals a similar condition has been noted. 



Large quantities of serum may be injected into man 

 almost daily, and extending to two or three weeks without 

 ill-effect. If, however, a period of twelve or more days 

 elapse between any two given injections, serious results are 

 liable to follow. The condition of the system is then 

 hypersensitive and is technically know as anaphylaxis, and 

 in some cases the result is fatal collapse. 



Theobald Smith noticed when guinea-pigs were injected 

 with horse serum and a second injection given after the 

 elapse of ten days, the pig will show signs of hypersensi- 

 tiveness, and if the dose is sufficient death may follow. 



Again, it has been shown that the sera obtained from one 



