400 THE SENSORIAL FUNCTIONS. 



attention, that the canal led to two glandular organs of an 

 oblong shape, and enclosed in cartilaginous tubes: each gland 

 has in its centre a cavity which communicates above with 

 the general cavity of the nostrils. These organs lie con- 

 cealed in a hollow groove within the bone, where they are 

 carefully protected from injury: and they receive a great 

 number of nerves and blood vessels, resembling in this re- 

 spect the organs of the senses. Their structure is the same in 

 all quadrupeds in which they have been examined; but they 

 are largest in the family of the Rodentia, and next in that 

 of the Ruminantia; in the Horse, they are still very large, 

 but the duct is not pervious; while, in carnivorous quadru- 

 peds, they are on a smaller scale. In Monkeys, they may 

 still be traced, although extremely small, appearing to form 

 a link in the chain of gradation connecting this tribe with 

 the human race, in whom every vestige of these organs has 

 disappeared, excepting the aperture in the bones already no- 

 ticed. Any use that can be attributed to these singularly 

 constructed organs must evidently be quite conjectural. 

 The ample supply of nerves which they receive would indi- 

 cate their performing some sensitive function; and their si- 

 tuation would point them out as fitting them for the ap- 

 preciation of objects presented to the mouth to be used as 

 food; hence it is probable that the perceptions they convey 

 have a close affinity with those of smell and taste. 



The larger cartilaginous fishes, as Sharks and Rays, have 

 been supposed by Treviranus to be endowed with a peculiar 

 sense, from their having an organ of a tubular structure on the 

 top of the head, and immediately under the skin; Roux con- 

 siders it as conveying sensations intermediate between those 

 of touch and hearing; while De Blainville and Jacobson re- 

 gard it merely as the organ of a finer touch. 



The perceptive powers of Insects must embrace a very 

 different, and, in many respects, more extended sphere than 

 our own. These animals manifest by their actions that they 

 perceive and anticipate atmospheric changes, of which our 

 senses give us no information. It is evident, indeed, that 



