ZOOLOGY. 



modifications. In the Whales it seems to be less adapted 

 for the purposes of smell than of respiration. The olfac- 

 tory nerves are in them very delicate, and the apex of 

 the nose is destitute of motion. 



In other beasts, on the contrary, it is elongated into a 

 very muscular proboscis or snout, and is endowed with 

 the power of voluntary motion. 



The form also of the nostrils is very varied, they being 

 round, narrow, patulous, and frequently capable of being 

 closed. 



3438. The tongue is indeed mostly fleshy and soft ; 

 yet in many species it is provided with horny points, in 

 others invested by a dense coriaceous tegument, so that 

 it appears to represent an instrument for deglutition 

 rather than gustation. 



3439. The lips also are mostly fleshy and moveable ; 

 yet in many they retrograde exceedingly and lose their 

 mobility, as is partly the case in the Ornithorynchus. 



3440. In most, however, the limbs, especially the toes, 

 are still subject to variation. Their perfection consists 

 in the number five, and in the difference between the 

 two pairs of limbs, as in Man. In the Apes the posterior 

 feet are also hands, which is an imperfection ; in the 

 Marsupials there are hands posteriorly but toes in front ; 

 in other respects there are generally toes, sometimes five, 

 then four, finally two perfect and two dew-claws in the 

 Ox, and at length only one in the Horse, while the pos- 

 terior extremities are virtually lost in the Whales. 



3441. The dental system, as being the set of max- 

 illary claws, is alone present in its state of perfection in 

 the Thricozoa. They alone have, in addition to the 

 incisor teeth, ah 1 the five kinds of teeth that differ from 

 each other in form, namely, canine, false molars, laniary, 

 with second and third true molars, corresponding to the 

 five fingers reckoned from the thumb. 



3442. In the dentition of those animals which tear 

 their food the greatest amount of completeness and variety 

 is met with, since each tooth has a different form and 

 function. 



