466 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1915. 



an extract of the cultures and the protoplasm of tuberculosis bacilli. 

 The results have been widely varying — often bad, sometimes favor- 

 able. It may be that at first too strong doses were used. In any 

 case the product has not the effect of vaccination and its therapeutic 

 use is not free from danger. 



The work of Wright especially has attracted attention to bac- 

 teriotherapy. The Wright vaccines are used against typhoid fever, 

 melitococcus, infections of streptococcus, and of staphylococcus. A 

 certain quantity of microbes killed by heating is injected into the 

 subject. ^Vlien it is possible a specimen taken from the sick person 

 himself is used, autovaccines producing appreciably better results. 

 By thus introducing bacterial products into a diseased organism the 

 cellular reactions are stimulated. Thus, by the indirect process of 

 favoring the development of an active immunity, the means of re- 

 sistance against infection are augmented. 



This brief summary shows the important results obtained by prac- 

 tical medicine from experimental researches. Prophylaxis and thera- 

 peutics have been completely revised by the vaccines and serums. 

 But it is important not to confound these two terms, and to distin- 

 guish clearly the methods which they designate. The word " vac- 

 cine " should be reserved for products of bacterial origin — that is, 

 for living microbes, weakened or modified — for bacterial autolysats, 

 and for soluble matter secreted by the bacteria. Serum, on the con- 

 trary, is a product of animal origin coming from an individual pre- 

 viously rendered immune. Vaccine arouses in the organism defensive 

 reactions; it creates an active immunity. Serum impregnates the 

 organism and establishes a passive immunity. 



Active immunity requires several days to develop, but lasts a long 

 time. Passive immunity is immediate, but quickly disappears. Vac- 

 cine is especially a prophylactic means, used more often to prevent 

 than to combat infection. Serum is at the same time a therapeutic 

 and a prophylactic medium. 



Thanks to serotherapy, mortality from infections and especially 

 from diphtheria has greatly diminished ; owing to vaccination, sick- 

 ness has declined. Smallpox, rabies, and anthrax have almost passed 

 out of existence, and the time can be predicted when other infections, 

 especially typhoid fever, will in their turn disappear. 



