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 
vonnected 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 papilla, which 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 papille given to thelatter. In 
some mammals the tongue is vermiform, long, and protractile ; in the leaf- 
nosed bat(Vampyrus phyllostoma) it is tubular, folded together, and also pro- 
vided at its extremity with projecting papille. 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 protectea 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 
(untitragus), serving 1n 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 papille-like projections: this is seen 
in the mole; the finger-like, elongated appendages of the proboscis of the 
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