68 E VOL UTION AND DISEASE. 



Sumatran rhinoceros. This animal, like all its kind, 

 has a large caecum, the distal extremity of which cor- 

 responds to the vermiform appendix, and derives its 

 blood-supply from the terminal twigs of a long ileo- 

 colic artery. The young animal to which these remarks 

 refer was sent to the Zoological Gardens, London ; at 

 the end of a few weeks it became sickly, refused food, 

 and finally died. At the autopsy it was discovered that 

 the lower jaw was extensively diseased, and a large 

 abscess had formed. This trouble offered satisfactory 

 explanation of the loss of appetite and inability to take 

 food. On examining the viscera, Mr. Frederick Treves 

 discovered the actual cause of death to be ulceration 

 and sloughing of the extremity of the caecum. In this 

 rhinoceros we have a similar condition of things to the 

 gangrene of the toes after typhoid fever, for the vital 

 powers being reduced by the trouble in the jaw, and the 

 inability to take sufficient food, those parts at the end 

 of the circulatory system suffered first, and the structure 

 most ready to succumb was the distal end of the caecum. 

 This case is very suggestive, because it teaches how, in 

 the process of evolution, so far as individual parts are 

 concerned, a limit is imposed upon the size attainable 

 by organs, and indicates the danger to which animals 

 are exposed in which particular vital organs attain in- 

 ordinate proportions. For instance, imagine two animals 

 living under similar conditions and upon the same kind 

 of food, but one has a moderate caecum, the other an 

 inordinately large one. Should a time of scarcity or 

 accident prevent such animals obtaining a proper 

 supply of nutriment, the one with an average caecum 

 (cceteris paribus) has the better chance of survival. 



