FECUNDITY. 115 



they breed at an earlier age, and at shorter intervals, 

 and produce a greater number of young at a birth. 



The elephant, the rhinoceros, the hippopotamus, 

 the camel, and the dromedary, produce but one at a 

 birth ; the cow, the red-deer, the sheep, the llama, the 

 mare, and the ass, produce one or occasionally two; 

 the goat, the roe-deer, and the chamois, produce two 

 or three; the cat, the fox, the jackal, the tiger, the 

 lion, and the bear, produce from two to six ; the dog 

 and the wolf, from five to ten ; the wild-boar, from 

 four to ten ; and the domestic sow, from eight to sev- 

 enteen ; while the smaller rodents have produced as 

 many as nineteen young at a birth. 



The larger animals, as the great pachyderms, the 

 solipeds, and the ruminants, breed but once a year; 

 while the smaller mammals breed two or three times 

 in a year. 1 



Among mammals, swine, and a few domesticated 

 varieties, present almost the only exceptions to the 

 prevailing inverse relation of size to fecundity. The 

 larger birds are less prolific than the smaller species, 

 while among the most minute members of the ani- 

 mal kingdom the most astonishing fecundity is ob- 

 served. 



In the cases of diminished fecundity from over- 

 feeding, or from an abnormal activity of the nutritive 

 functions, a plethoric condition of the system is pro- 

 duced that may, in itself, impair the vigor of the re- 

 productive powers, or lead to the development of local 



1 Colin, "Physiologic comparee," tome ii., p. 531 ; Spencer's "Prin- 

 ciples of Biology," vol. ii., pp. 435, 436; "Animals and Plants under 

 Domestication," vol. ii., p. 139. 



