446 MICROORGANISMS 



knowing that the organism can be killed in the human 

 system by the use of quinine, we are in a splendid position to 

 combat the disease and it is surely possible to completely 

 eradicate it in many places. If all persons suffering with 

 malaria in a given locality were promptly and completely 

 cured by the use of quinine, the mosquitos could do no harm 

 for they could not become infected. On the other hand, if all 

 Anopheles mosquitos in the locality were destroyed, no one 

 could contract malaria from those suffering with it. It is 

 probably best to make use of both of these methods at the 

 same time. The parasite is able to linger in the human 

 body for many months if it is not eradicated by quinine. Dur- 

 ing this time, the patient is likely to be fairly well part of the 

 time and then to have repeated relapses. In this way, a 

 few people in every malarial district carry the organism over 

 winter while the mosquitos are not active and give the 

 disease a fresh start when the mosquitos return. Con- 

 sequently, the winter time is an important time for the treat- 

 ment of malarial patients. 



518. Other Diseases. There are several other diseases 

 which have been quite thoroughly studied and more or less 

 mastered by bacteriologists but they are either unimportant 

 or else occur so seldom in the United States as not to warrant 

 discussion here. Among these are the bubonic plague and 

 plague pneumonia, leprosy and Asiatic cholera. 



III. DISEASES WHOSE CAUSES ARE UNKNOWN 



We have several very common contagious diseases which 

 from all appearances are due to bacteria or to microorganisms, 

 and yet they have so baffled all efforts to determine their 

 cause with certainty. In this list is included smallpox which 

 we have already discussed sufficiently. We shall mention 

 the others only briefly. 



519. Rabies or Hydrophobia. This disease in the human 

 being generally results from the bite of a dog or other animal 



