FUNCTIONS OF THE BRAIN. 399 



Bats have been supposed to possess a peculiar, or sixth 

 sense, enabling them to perceive the situations of external ob- 

 jects without the aid either of vision or of touch. The prin- 

 cipal facts upon which this opinion has been founded were 

 discovered by Spallanzani, who observed that these animals 

 would fly about rapidly in the darkest chambers, although 

 various obstacles were purposely placed in their way, with- 

 out striking against or even touching them. They continued 

 their flight with the same precision as before, threading their 

 way through the most intricate passages, when their eyes 

 were completely covered, or even destroyed. Mr. Jurine, 

 who made many experiments on these animals, concludes 

 that neither the senses of touch, of hearing or of smell, were 

 the media through which bats obtain perceptions of the pre- 

 sence and situation of surrounding bodies; but he ascribes 

 this extraordinary faculty to the great sensibility of the skin 

 of the upper jaw, mouth, and external ear, which are fur- 

 nished with very large nerves.* 



The wonderful acuteness and power of discrimination 

 which many animals exercise in the discovery and selection 

 of their food, has often suggested the existence of new senses, 

 different from those which we possess, and conveying pecu- 

 liar and unknown powers of perception. An organ, which 

 appears to perform some sensitive function of this kind, has 

 been discovered in a great number of quadrupeds by Jacob- 

 son. t In the human skeleton there exists a small perfora- 

 tion in the roof of the mouth, just behind the sockets of the 

 incisor teeth, forming a communication with the under and 

 fore part of the nostrils. This canal is perceptible only in 

 the dried bones; for, in the living body, it is completely 

 closed by the membrane lining the mouth, which sends a 

 prolongation into it: but in quadrupeds, this passage is per- 

 vious even during life, and is sometimes of considerable 

 width. Jacobson found, on examining this structure with 



* Sir Anthony Carlisle attributes this power to the extreme delicacy of 

 hearing in this animal. 



f See Annales du Musee; xviii. 412. 



