394 ZOOLOGY. 



of defence ; and they are often used during the pairing season in violent 

 and sometimes fatal combats between the males. After this season is over, 

 absorption takes place at the point where the horn joins the boss or frontal 

 process, and at length falls off, to be renewed again in due time. Such 

 is this remarkable process in deer generally ; the period at which it takes 

 place varies according to the species." 



Several mammals have on their faces membranous appendages, or else 

 prominent folds of the skin, as, for example, on the nose of some bats. The 

 lips in mammals are generally fleshy, the upper one sometimes fissured, and 

 in a few cases even entirely wanting. The tongue, fleshy and movable, is 

 connected with a bone called the hyoid, which is composed of several pieces, 

 and suspended to the cranium by ligaments. The upper surface of the tongue 

 possesses small warts or papillae, wjiich are generally blunt and soft, but in 

 some genera are acute and more or less hardened. The nerves of taste extend 

 to these papillae, whence the name of nervous papillae given to the latter. In 

 some mammals the tongue is vermiform, long, and protractile ; in the leaf- 

 nosed ha.i{Vampyrus phyllostomd) it is tubular, folded together, and also pro- 

 vided at its extremity with projecting papillse. The giraffe can protrude the 

 tongue considerably, and by this means take hold of surrounding objects. 



In some mammals the nose grows into a proboscis ; in others, on the 

 contrary, it is very little or not at all apparent. Many kinds which live in 

 water can shut the nostrils, or openings of the nose, when diving. The 

 nostrils in the whale are on the top of the head, and in some of them they 

 open exteriorly by a single opening. The sense of smell is more or less 

 developed in mammals. 



The eyes, invariably lodged in an orbit, are protected by two or three 

 lids. They are of different sizes ; in some very small, even hidden under 

 the epidermis, as, for instance, the blind mouse {Spalax typhlus). The 

 pupil is generally circular ; but in some animals, as in cats, foxes, &c., it is 

 elongated vertically, while in others the elongation is horizontal. The eyes 

 are furnished with eye-lashes. Many ruminants have a lachrymal opening 

 at the inner angle of the eye ; at least, there exists a cavity which secretes 

 a fatty and black (often hardened) substance. 



The size of the ear-opening, as well as that of the concha itself, is very 

 variable; the latter sometimes is entirely wanting; where it exists, it is 

 either erect, or hangs partially or completely down ; the animal can also 

 direct it more or less towards the place whence a sound comes. Most of 

 the bats have before the ear an erect membrane, which is called ear-cover 

 (antitragus), serving in a measure to this purpose. The seals have a similar 

 adaptation, although less conspicuous. The ears of many other mammals 

 can also be shut. The bats appear to possess a very delicate sensibility in 

 the membrane of the ear, which is furnished with an abundance of nerves, 

 as well as in the membrane of the wings. 



In most of the mammals the snout and toes perform the functions of pre- 



hensory organs ; in the proboscidians, it is the proboscis. The snout, .in 



some cases, is provided with peculiar papillae-like projections : this is seen 



in the mole ; the finger-like, elongated appendages of the proboscis of the 



598 



