98 MAMMALIA. 



the thiclmess and fineness of whicli increases witli the severity 

 of the climate they inhabit, and which is covered by rather coarse 

 hairs lubricated with oil, the object of which is to prevent the 

 water from penetrating to the skin. A thick layer of fat protects 

 the body against the cold, more especially in those species which 

 inhabit the extreme frigid regions. 



The Amphibia have the head rounded, the eyes large, the 

 auditory conch rudimentary or null, the upper lip covered with a 

 thick moustache. Their jaws have three sorts of teeth, and the 

 brain is furrowed into numerous circumvolutions. Living in 

 numerous troops, thej' feed on Fishes, MoUusks, Crustaceans, &c. 

 They dive with great facility ; and although obliged to come to 

 the surface to breathe they can remain a long while under water. 

 This circumstance is explained by a peculiarity in their circulating 

 apparatus. They are provided with vast venous reservoirs, m 

 which the blood accumulates whilst the lungs are inactive. The 

 animal is not suffocated on that account, however ; for asphyxia, or 

 suffocation, is brought on by the stoppage of the circulation of the 

 blood, as soon as respiration is suspended; but the sinus provides 

 this circulation in the pulmonary ceUs whilst the animal is under- 

 neath the surface. 



Owing to this precaution of nature, the Amphibia can wander 

 freely about in the depths of the ocean in search of their 

 food ; it is only when the blood overruns their venous reser- 

 voirs that they find it necessarj^ to remount to the surface to 

 breathe. 



As their members are badly fitted for locomotion on land [hi 

 most instances], the Amphibia only leave the water when they 

 want to sleejD, to give birth to or suckle their young. Under 

 such circumstances, when they are siirprised on the shore, they 

 are quite at the mercy of their assailants ; for they are equally 

 incapable of escaping from, and of resisting those who attack 

 them. One must not be surprised, then, that considerable quan- 

 tities of these animals are destroyed every year, and that the 



unwieldy and awkward on land, where its movements forcibly remind the spectator 

 of the wrigglings of a gentle or fiy-maggot ; hut it makes considerahle use of its 

 hind-legs, hy hringing them forward and thus taking hold of the ground ; whereas, 

 those of the Seals are more directed backwards. Wlien in the water, and about 

 to dive, both the Walrus and the Sea-bears show their backs above the surface, Kke 

 a Porpoise, but this is never observed of the true Seals. — Ed. 



