INFECTIOUS DISEASES AND MICROBES, ETC. 215 



experiments on mice and rabbits to act as a com- 

 plete cure. Kitasato's experiments prove (a) that 

 the blood of rabbits which have been rendered un- 

 susceptible to tetanus possesses properties destruc- 

 tive of the tetanus virus ; (&) that these properties 

 are to be observed also in extra-vascular blood and 

 serum free from cells ; (c) that these properties are 

 of so permanent a nature that they are still mani- 

 fested by such serum after it has been injected into 

 other animals ; consequently, by transfusion of such 

 blood or serum, important therapeutic actions can 

 be obtained ; (d) that this power of destroying the 

 tetanus poison is absent from the blood of such 

 animals as are not immune against tetanus; and 

 after such animals have been killed by the tetanus 

 poison, it can be shown to be present in their blood 

 and tissues. 



If animals (such as mice and rabbits) highly sus- 

 ceptible to tetanus are cured by this treatment, we 

 have good reason to believe that it will also cure 

 human beings, which are far less susceptible to the 

 disease. 



MALARIA. 



The discovery of the Bacillus malarice placed 

 malaria among the acute specific diseases. Concern- 

 ing the distribution of malaria, moisture and air 

 have much to do with it, for the disease is more 

 abundantly developed in wet than in dry years. 

 Moisture in the soil is essential for the production 

 of malaria, while clayey, loamy, and marshy soils 



