BIOLOGICAL SCIENCE 65 



still exists, but it is no longer infected by the specific 

 parasite. Thus it seems possible to look forward 

 to the entire elimination at some time of any one 

 particular microbe, and so to remove its character- 

 istic disease from among the human race. 



The success which attended the researches on 

 malaria has led to an extension of this branch 

 of preventive medicine in many directions. The 

 ravages of Mediterranean or Maltese fever among 

 the troops and crews of the men-of-war stationed in 

 those regions led to the appointment of a committee 

 of inquiry. A specific organism causing the disease 

 was again discovered ; and it was found that it 

 spent one of the necessary stages of its existence 

 in the goats, which form an important part of he 

 economic wealth of the Mediterranean agriculturist. 

 Thence the infection is transferred to men in the milk, 

 butter, or cheese derived from these animals. The 

 goats themselves, however, show no signs of feeling 

 any discomfort from the presence of the parasite. 

 This immunity of the animal host from any obvious 

 form of disease constitutes one of the most baffling 

 features in the pursuit of this class of knowledge. 



Whole districts of Central and East Africa are 

 ravaged by epidemics and maladies in man and 

 beast, such as sleeping sickness, blackwater fever, 

 and others, by which some areas have been rendered 

 almost uninhabitable ; and various animals, pre- 

 viously unsuspected, have been shown to play their 



