508 THE SENSORIAL FUNCTIONS. 



The wonderful acuteness and power of dis- 

 crimination 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 

 peculiar and unknown powers of perception. 

 An organ, which appears to perform some sen- 

 sitive function of this kind, has been discovered 

 in a great number of quadrupeds by Jacobson.* 

 In the human skeleton there exists a small per- 

 foration in the roof of the mouth, just behind the 

 sockets of the incisor teeth, forming a communi- 

 cation with the under and fore part of the nos- 

 trils. Tliis 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 pervious, even during life, and is 

 sometimes of considerable width. Jacobson 

 found, on examining this structure with atten- 

 tion, that the canal led to two glandular organs 

 of an oblong shape, and enclosed in carti- 

 laginous tubes : each gland has in its centre a 

 cavity, which communicates above with the 

 general cavity of the nostrils. These organs lie 

 concealed in a hollow groove within the bone, 

 where they are carefully protected from injury : 

 and they receive a great number of nerves and 



* See AniiLiles tlu Musec; xviii. 412. 



