400 THE ETIOLOGY OF TROPICAL DISEASES 



or tuberculosis, but has striking etiological analogies with the 

 latter. 



" 2. Leprosy is not diffused by hereditary transmission, and, for 

 this reason and the established amount of sterility among lepers, the 

 disease has a natural tendency to die out. 



" 3. Though in a scientific classification of diseases, leprosy must 

 be regarded as contagious, and also inoculable, yet the extent to 

 which it is propagated by these means is exceedingly small. 



" 4. Leprosy is not directly originated by the use of any particular 

 article of food, nor by any climatic or telluric conditions, nor by 

 insanitary surroundings, neither does it peculiarly affect any race 

 or caste. 



" 5. Leprosy is indirectly influenced by insanitary surroundings, 

 such as poverty, bad food, or deficient drainage or ventilation, for 

 these by causing a predisposition increase the susceptibility of the 

 individual to the disease. 



" 6. Leprosy, in the great majority of cases, originates de novo, 

 that is, from a sequence or concurrence of causes and conditions dealt 

 with in the Eeport, and which are related to each other in ways at 

 present imperfectly known." 



The practical suggestions of the Commission for preventive 

 treatment included voluntary isolation, prohibition of the sale of 

 articles of food by lepers, leper farms, orphanages, and "improved 

 sanitation and good dietetic conditions " generally. Serum-therapy 

 has been attempted on behalf of the French Academy of Medicine, 

 but without success. Many forms of treatment ameliorate the 

 miserable condition of the leper, but up to the present no curative 

 agent has been found. 



5. Yellow Fever 



This disease is admitted to be one of the most terrible of tropical 

 diseases. Fortunately, its area of endemicity is comparatively 

 limited. "When, however, it breaks out, especially on board ship, 

 its high percentage of fatality is well known. 



A number of investigators, from the beginning of last century 

 down to the present time, have been at work on the cause of yellow 

 fever. Sanarelli, the Director of the Institute of Hygiene, in the 

 University of Montevideo, in South America, is one of the more 

 recent workers, and he has isolated a bacillus which he believes is 

 the causal agent of the disease. The bodies of those who die of 

 yellow fever are, however, either so free from organisms, or so entirely 

 invaded by organisms, that the £. icteroides is difficult to discover. 

 Moreover, led by the clinical signs of the disease — " black vomit " and 

 other gastro-intestinal phenomena — investigators have, a priori, 

 supposed that the digestive canal was the seat of the disease, and 



