A CURIOUS EXPERIENCE 333 



the point that seems to invite the disease. The 

 porcupines are rather unsocial, and are so le- 

 thargic in their movements that the infection 

 took longer to do its full work. But this work 

 was done so thoroughly that evidently the entire 

 race of porcupines over a large tract of country 

 was exterminated. Porcupines have few foes 

 that habitually prey on them, although it is 

 said that there is an exception in the shape of the 

 pekan — the big, savage sable, inappropriately 

 called fisher by the English-speaking woods- 

 men. But they breed so slowly (for rodents) 

 and move about so little that when exter- 

 minated from a district many years elapse be- 

 fore they again begin to spread throughout it. 

 The rabbits, on the contrary, move about so 

 much that infectious diseases spread with ex- 

 traordinary rapidity and they are the habitual 

 food of every fair-sized bird and beast of 

 prey, but their extraordinary fecundity enables 

 them rapidly to recover lost ground. As re- 

 gards these northern wood-rabbits, and doubt- 

 less other species of hares, it is evident that their 

 beast and bird foes, who prey so freely on their 

 helplessness, nevertheless are incompetent to 

 restrain the overdevelopment of the species. 

 Their real foes, their only real foes, are the 

 minute organisms that produce the diseases 



