In the construction of the snout of the Tapir the arrangement of the nasal cartilages and muscles of the nose is still more elaborate, forming a rudimentary proboscis which is only surpassed in complexity by the trunk of the Elephant, the only existing type of the true Proboscidian Mamnaalia : in fact it is con structed upon the same principles, the great difference consisting in the diminutive size of the ouran in the Tapir when contrasted with the prodigious dimensions of the corresponding parts in the Elephant's proboscis. The nose of the Tapir is composed of' two menabranous tubes, ainply provided with mucous lacunw, and en closed in a fleshy mass surrounded by the skin, which consists of longitudinal muscles that take their origin beneath the lower margin of the orbit, and of fasciculi of transverse fibres passing be tween the skin and the external surface of the membranous nasal tubes. There is a pair of muscles in every way similar to the elevators of the upper lip of the Horse, derived from the pre cincts of the orbit, and uniting into a common tendon to bd inserted into the upper aspect of the nose, a pair of depressors arising from the intermaxillary bones, and also a slip derived from the occipito-frontalis, which is implanted by the intervention of a tendon into the base of the proboscis.
The proboscis of the Elephant, the only existing example of a completely developed nasal apparatus, forms an elongated cone of four or five feet in length, and gradually ta:per ing from the root towards the point, which is terminated by a kind of thumb-like appendage which is endowed with exquisite sensibility, so as to be useful in picking up the smallest objects. Internally the Elephant's trunk is perforated by a double tube, formed by a strong tendinous membrane, through which in numerable mucous crypts pour fluid abundantly into the nose. The membranous tubes are continued upwards as far as the bony nostrils, but, a little before their junction with the latter, they form two curves, the nasal passages being closed at this point by a cartilaginous elastic valve, which may be opened at the will of the animal, but closes by its own elasticity when the muscles which open it cease to act.
All the interval between the membranous tubes which follow the axis of the proboscis, and the skin by which it is invested externally, is filled up with a thick layer of muscular substance composed of two sets of fibres. Of these one set passes from the exterior of the membranous tubes to a strong tendinous mem brane situated immediately beneath the skin in such a way that on making a transverse section of the trunk, these muscles represent the radii of a circle : their action- will be, of course, to approximate the membranous tubes and the external integument of the trunk, and thus by compressing the intervening space, their con traction will have the effect of elongating the whole proboscis, without at the same time diminishing the calibre of the membranous tubes, as would have been the case had annular fibres been employed instead of this remarkable arrangement.
The other muscles of the proboscis are disposed longitudinally, and form a multitude of fasci cull, disposed in short curves in such a manner that the two extremities of each fasciculus are implanted into the membranous tubes, while the convexity of the arch is adherent to the external tendinous membrane. These fasciculi surround the whole trunk, and extend along its entire leng,th ; their effect being to shorten it from end to end or in any part the animal may please. It is evident that by these partial elongations or shortenings of one side or the other, the Elephant can bend its trunk in any direction with the utmost ease, and make use of it as efficiently as a hand in the performance of many Important offices. In addition to the above account of .the anatomy of this remark able apparatus given by the Parisian Acade micians, Cuvier ascertained that all the longitu dinal fasciculi which enter into the composition of the trunk are derivations from four great muscles, which, though almost blended together in the trunk itself, are distinct enough near their commencements. Of these the two ante rior arise from the whole breadth of the frontal bone above the ossa nasi, while the two lateral muscles take their origins from the superior maxillary bones beneath and in front of the orbit. The posterior or inferior aspect of the Elephant's proboscis is covered with fibres, which seem to be continuations of the orbicu laris oris, and which run obliquely downwards and inwards so as to meet their fellows from the opposite side at an acute angle. With such a structure it is evident that the nasal prolongation of the Proboscidian Pachyderms as able to move in every needful direction, and perform all the duties of a lithe and flexible arm, strong enough to tear the branches from the trees, and sufficiently manageable to be avail able for the most delicate manipulatioris.
The instruments of the senses present few peculiarities.
In connection with the organs of smell we may conveniently mention the sinuses which communicate with the nasal cavities, which in many Pachydermata are extremely developed. The frontal sinuses of the Elephant are of enormous extent, reaching throughout all the thickness of the frontal, of the parietal, of the temporal, and even extending into the condyles of the occiput. The whole of this extensive cavity is divided into cells by numerous imper fect septa, irregularly disposed. In the Hog tribes they are equally extensive, but far more shallow; they reach as far back as the occiput, and are divided into communicating cells by longitudinal or slightly oblique lamellx of bone. In the Babiroussa there are four rows of such cells, and in the common Hog seven or eight. In the Hippopotamus and Rhinoceros the fron tal sinuses can scarcely be said to exist.