A Round-up of Undesirables 137 



usually the dog. The nature of the infective 

 agent is unknown. It is apparently not 

 bacterial. Learned folks guess it to be a 

 protozoan. 



But nevertheless here, as in smallpox, a 

 most effective method of prevention has been 

 devised by Pasteur, so that one bitten by a 

 mad dog has the best of chances to escape the 

 disease if he will but promptly apply for 

 treatment to the appropriate laboratories 

 maintained by health departments and others. 

 The nature of the preventive treatment in 

 hydrophobia is considered briefly elsewhere in 

 this book. 



Malaria 



This wearisome malady is not induced by 

 bacteria and so is only smuggled in here to 

 round out the census of common infections. 

 It is due to a tiny animal, a protozoan, which 

 is conveyed from the sick to the well through 

 the bite of a particular species of mosquito 

 called Anopheles. The germ itself is named 

 Plasmodium malar ice. It takes the two of 



