254 E VOL UTION AND DISEASE. 



frog, its temperature be raised to 36 by carefully warm- 

 ing the water in which the frog is placed it will succumb. 



Such facts as these throw great light upon the re- 

 striction of diseases to particular groups of animals, and 

 it explains the readiness with which the tubercle bacillus 

 flourishes in man, for experimentally it has been found 

 to develop most luxuriously at a temperature of 37 to 

 39 Cent. This would serve to explain the rarity of 

 tubercular lesions in cold-blooded animals. 



Up to the present time tubercle has only twice been 

 recorded in reptiles. The first specimen I observed in a 

 large Python (Python molurus). The nodules in the 

 various organs contained bacilli in large numbers. In 

 this instance I am of opinion that the reptile contracted 

 the disease from eating tubercular birds. Mr. W. K. 

 Sibley reported a case of tuberculosis which he found in 

 a snake (Tropidonotus natrix). As the tubercle bacillus 

 flourishes at a temperature of 37-39 Cent, it at first 

 seems difficult to account for tubercular lesions in snakes. 

 In a valuable series of observations made by Mr. 

 Forbes 1 on an incubating python at the Zoological 

 Gardens, the temperature of the male was found to 

 vary from 28-3O C. ; the temperature of the female 

 under the same conditions of external warmth was 

 29-3r6 C. These observations were made in July, 

 and the greatest temperature recorded between the folds 

 of the male was 32 C. ; for the female, 33-8 C. It is 

 also of interest to find that the temperature of the 

 pythons, taken between the folds, was higher than the 

 surrounding air, sometimes as much as 6*4 C. in the 

 1 " Collected Papers, 1885," p. 285. 



