1 66 NATURE STUDIES. 



governs the actions in the same way, though not so 

 obviously,, as sight governs them in most of the 

 actions of later years. 



The next case cited also relates to the apparent 

 exercise of reasoning faculties by rats, and is inter- 

 esting, because probably their action was guided by 

 the sense of hearing, rather than by that of smell. 

 " Some years ago," says the narrator, " a plumber 

 told me that he had, on several occasions, been called 

 in to examine into the cause of leakage of water-pipes 

 under the flooring of houses, and had found that the 

 rats had gnawed a hole in the leaden pipe to obtain 

 water, and that great numbers of them had made it a 

 common drinking-place, as evidenced by the quantity 

 of dung lying about. The plumber brought me a 

 piece of leaden pipe, about three quarters of an inch 

 in diameter, and one-eighth of an inch in thickness, 

 penetrated in two places, taken by himself from a 

 house on Haverstock-hill. There are the marks of the 

 incisors on the lead as clear as an engraving ; and a 

 few hairs and two or three of the rat's whiskers have 

 been pinched into the metal in the act of gnawing it. 

 This crucial proof of brute intelligence for a rat will 

 not drink foul water interested me so much that I 

 ventured to send an account of it to Dr. Charles Dar- 

 win, asking his opinion on the means by which the 

 rats ascertained the presence of water in the pipe. 

 To this he replied : ' I cannot doubt about animals 

 reasoning in a practical fashion. The case of the rats 

 is very curious. Do they not hear the water trick- 



