SENSATION. 93 



tory sense ; and it is not until he has himself seen the deer 

 scent him at some almost incredible distance that he lends 

 himself without disguised contempt to the discretion of the 

 keeper. But among the Carnivora the sense of smell is even 

 more extraordinary in its development on account, no doubt, 

 of its being here of so much service in tracking prey. I 

 once tried an experiment with a terrier of my own which 

 shows, better than anything that I have ever read, the almost 

 supernatural capabilities of smell in Dogs. On a Bank 

 holiday, when the broad walk in Eegent's Park was swarm- 

 ing with people of all kinds, walking in all directions, I took 

 my terrier (which I knew had a splendid nose, and could 

 track me for miles) along the walk, and, when his attention 

 was diverted by a strange dog, I suddenly made a number of 

 zig-zags across the broad walk, then stood on a seat, and 

 watched the terrier. Finding I had not continued in the 

 direction I was going when he left me, he went to the place 

 where he had last seen me, and there, picking up my scent, 

 tracked my footsteps over all the zig-zags I had made until 

 he found me. Now in order to do this he had to distinguish 

 my trail from at least a hundred others quite as fresh, and 

 many thousands of others not so fresh, crossing it at all angles. 



Such being the astonishing perfection of smell in dogs, it 

 has been well observed that the external world must be to 

 these animals quite different from what it is to us ; the 

 whole fabric of their ideas concerning it being so largely 

 founded on what is virtually a new sense. But in this con- 

 nection I may point out that speculation on such a subject is 

 shown to be useless by the fact that the sense of smell in 

 dogs does not appear to be merely our own sense of smell 

 greatly magnified. For if this were the case it seems incredible 

 that highly bird sporting-dogs, which have the finest noses, 

 should be those which take the keenest pleasure in rolling in 

 tilth which literally stinks in our nostrils to the degree of 

 being physically painful, 



The sense of hearing is acute in Mammals as a class, and 

 it is worthy of remark that this is the only class provided 



With movable ears. As 1'aley observes, in beasts of prey the 



external ear is habitually directed forwards, while in species 

 which the} prey upon the ear admits of being directed hack- 

 wards. With the exception <>i the singing monkey {Hylobatea 

 agilis), there is no evidence of any mammal other than man 

 5 



