482 WILD ANIMALS. 



A seal's head bears some resemblance to that of a dog, or rather 

 of an otter, for it is short and broad, and is provided with stiff 

 and thick whiskers, which are evidently used as organs of touch, 

 for the root of each bristle is connected with a highly sensitive 

 nerve, as it is in the carnivorous order of land animals. The 

 dental formula is not the same in all species, but they all have 

 teeth adapted for the seizure and retention of their slippery prey. 

 The eyes are large and brilliant. The ears are inconspicuous cavi- 

 ties, which are provided with small perfectly- fitting valves, that 

 enable them to be closed or opened as required, and the sense of 

 hearing seems to be very acute. 



The respiration of the seal family is extremely slow, and not only 

 slow, but very irregular ; for when on land and moving about, they 

 will be observed to take a breath perhaps once in every two 

 minutes, but in the water they can remain without breathing for 

 over twenty minutes. Ouvier noticed the seals that were kept in 

 the menagerie at Paris remained asleep with their heads under 

 water, and consequently without the power of breathing, for 

 upwards of an hour. Their ability to suspend respiration for so 

 long a period enables them to make long pursuits after their prey. 



A seal's nostrils are also closed with a sphincter-like muscle, 

 whose use was described in the case of the camels. In these latter 

 animals, it was employed to exclude the sand ; in the partially 

 amphibious animals, however, it effectually closes the apertures 

 against the water — a provision which is absolutely necessary to 

 them, for they spend such a large portion of their lives in that 

 element, and take, their food there ; for although they can eat on 

 land, the seal family generally eat when beneath the surface. 



The thick soft fur that covers the skin prevents sudden changes 

 of temperature from affecting them, and aids in the retention 

 of the heat of the body. This last object is also assisted by the 

 thick layer of subcutaneous fat which covers the bones, and which 

 also serves to make the specific gravity of the animal nearly as 

 light as the water in which it passes so much of its time. 



Mr, J. A. Allen, in his able monograph of the North American 

 Pinnipeds, published by the Department of the Interior of the 

 United States Government, gives such full and accurate de- 



