and the bottom of the cavity of the nose: this is intersected by a more perpendicular one, proceeding from the convexity of the forehead to the most prominent point of the upper jaw, or of the intermaxillary bone. The latter is the proper facial line; and the angle which it forms with the horizontal line determines, according to Camper, the differences of the crania of animals, as well as the national physiognomy of the various races of man. kind.

The two organs which occupy most of the face are, those of smelling and tasting, (including those of mastication, &c.) In proportion as these parts are more developed, the size of the face, compared to that of the cranium, is augmented. On the contrary, when the brain is large, the volume of the cranium is increased in proportion to that of the face. A large cranium and small face indicate therefore a large brain, with inconsiderable organs of smelling, tasting, masticating, &c.; while a small cranium, with a large face, shew that these proportions are reversed.

The nature and character of each animal must depend considerably on the relative energy of its different functions. The brain is the common centre of the nervous system. All our perceptions are conveyed to this part, as a sensorium commune: and this is the organ by which the mind combines and compares these perceptions, and draws inferences from them; by which, in short, it reflects and thinks. We shall find that animals partake in a greater degree of this latter faculty, or at least approach more nearly to it, in proportion as the mass of medullary substance, forming their brain, exceeds that which constitutes the rest of the nervous system; or, in other words, in proportion as the organ of the mind exceeds those of the senses. Since then the relative proportions of the cranium and face indicate also those of the brain and the two principal external organs, we shall not be surprised to find that they point out to us, in great measure, the general character of animals, the degree of instinct and docility which they pos

sess.

Man combines by far the largest cranium with the smallest face; and animals deviate from these relations, in proportion as they increase in stupidity and ferocity.

One of the most simple methods (though sometimes indeed insufficient) of expressing the relative proportions of these parts, is by means of the facial line,

which has been already described. This angle is most open, or approaches most nearly to a right angle, in the human sub. ject; it becomes constantly more acute, as we descend in the scale from man; and in several birds, reptiles, and fishes, it is lost altogether, as the cranium and face are completely on a level. The idea of stupidity is associated, even by the vulgar, with the elongation of the snout; hence the crane and snipe have become proverbial. On the contrary, when the facial line is elevated by any cause which does not increase the capacity of the cranium, as in the elephant and owl, by the cells which separate the two tables, the animal acquires a particular air of intelligence, and gains the credit of qualities which he does not in reality possess.

Hence the latter animal has been selected as the emblem of the goddess of wis dom. The invaluable remains of Grecian art shew that the ancients were well ac quainted with these circumstances; they were aware, that an elevated facial line formed one of the grand characters of beanty, and indicated a noble and generous nature. Hence they have extended the facial angle to 90 degrees in the represen tation of men, on whom they wished to bestow an august character. And in the representation of their gods and heroes, they have even carried it beyond a right angle, and made it 100°.

It must, however, be allowed, that the facial angle is of chief importance in its application to the cranium of the human subject, and of the quadrumana: as vari ous circumstances affect the conclusions which would result from employing it in other classes of mammalia. Thus, in the carnivorous, and some of the ruminating animals; in the pig, and particularly in the elephant, the great size of the frontal sinuses produces an undue elevation of the facial line. In many of the rodentia, as the hare, &c. the nose occupies so large a space, that the cranium is thrown quite back, and presents no point on a front view, from which this line can be drawn.

The following are the angles formed by drawing a line along the floor of the nos trils, and intersecting it by another, which touches the anterior margin of the upper alveoli, and the convexity of the cranium, (whether the latter point be concealed by the face or no;)

In the third and fourth tables of Cuvier's "Tableau Elementaire del'Histoire Naturelle," the crania of several mammalia are represented in profile, so as to afford a sufficient general notion of the varieties in the facial angle. A similar comparative view, in one plate, is given by White, in his account of the "Regular Gradation," &c. from the work of Camper.

A vertical section of the head, in the longitudinal direction, shews us more completely the relative proportions of the cranium and face. In the European, the area of the section of the cranium is four times as large as that of the face; the lower jaw not being included. The proportion of the face is somewhat larger in the negro and it increases again in the orangoutang. The area of the cranium is about double that of the face in the monkeys; in the baboons, and in some of the carnivorous mammalia, the two parts are nearly equal. The face exceeds the cranium in most of the other classes. Among the rodentia, the hare and marmot have it one third larger; in the porcupine and the ruminantia, the area of the face is about double that of the cranium; nearly triple in the hippopotamus; and almost four times as large in the horse. In rep. tiles and fishes, the cranium forms a very inconsiderable portion of the section of the head, although it is considerably larger than the brain which it contains.

The outline of the face, when viewed in such a section as we have just mentioned, forms in the human subject a triangle, the longest side of which is the line of junction between the cranium and face. This extends obliquely, backwards and downwards, from the root of the nose towards the foramen occipitale. The front of the face, or the anterior line of the triangle, is the shortest of the three. The face is so much elongated, even in the simiæ,

that the line of junction of the cranium and face is the shortest side of the triangle, and the anterior one the longest. These proportions become still more considerable in other mammalia.

The upper jaw-bones of other mammalia do not, as in man, touch each other under the nose, and contain all the upper teeth; but they are separated by a peculiar, single, or double intermaxillary bone, which is in a manner locked between the former, and holds the incisor teeth of such animals as are provided with these teeth. It exists also in the pecora, which have no incisor teeth in the upper jaw; as well as in such genera as have no incisor teeth at all; viz. the duck-billed animal and the armadillo. It is even found in those mammalia which are wholly destitute of teeth; as the ant-eater and the proper whales. It is joined to the neighbouring bones by sutures, which run exteriorly by the side of the nose and snout, and which pass towards the palate, close to the foramina incisiva. Its form and magnitude vary surprisingly in several orders and genera of mammalia. It is small in many fere; as also in the walrus. In the glires it is remarkably large, on account of the immense size of their incisor teeth.

In human crania, at least those of the fœtus and young children, there is a small transverse slit near the foramen incisivum, of which Fallopius gave the following accurate account in the year 1561: "I find this division to be rather a slit than a suture, since it does not separate one bone from the other, nor does it appear exteriorly, nor join two bones, which is the office of sutures." "Obs. Anat."

"Hence I was much surprised to find Vicq D'Azyr, in 1780, discover in this point an unexpected resemblance between the cranium of the human subject and of quadrupeds." Mem. de l'Acad. des Sc. 1780.

In the celebrated dispute of the sixteenth century, whether Galen's osteology was derived from the skeleton of man or the ape, Ingrassias argued for the latter side of the question, from Galen's having ascribed an intermaxillary bone to the human subject. And the same author, in his classical "Commentarii in Galeni Li. brum de Ossibus,” Panorm, 1603, fol. particularly points out the parts, "where Galen, led astray by the dissection of apes, deviates from the true construction of the human body,”

In mammalia which have horns, these parts grow on particular processes of certain bones of the cranium. In the onehorned rhinoceros, they adhere to a rough and slightly elevated surface of the vast nasal bone. The front horn of the twohorned species has a similar attachment; the posterior rests on the os frontis, as those of the horned pecora do. Two kinds of structure are observed in the latter; there are either proper horns, as in the genera of the ox, goat, and antelope; or bony productions, as in the genus cervus, which includes animals of the deer kind: these are also called horns in English, or sometimes antlers; in French, bois de cerf. In the former, the external table of the frontal bones is elongated into a process, which contains a continuation of the frontal sinuses, except in the antelope. Its external vascular surface secretes the horn, which covers this process like a sheath. In the stag kind (in the male only in most genera) the frontal bone forms a short flattened prominence, from which the proper antler immediately shoots forth. It is renewed every year, and is covered, during the time of its growth, with a hairy and very vascular skin.

Castration, or any essential injury of the organs of generation,impedes the growth, alters the form, or interrupts the renewal of the horns.

The word horn, which is frequently applied in English to the antlers of the deer kind, as well as to the real horns of other genera, would lead to a very erroneous notion on this subject. The antler is a real bone; it is formed in the same manner, and consists of the same elements as other bones; its structure is also the

same.

It adheres to the frontal bone by its basis; and the substance of the two parts be. ing consolidated together, no distinction can be traced, when the antler is completely organized. But the skin of the forehead terminates at its basis, which is marked by an irregular projecting bony circle; and there is neither skin nor periosteum on the rest of it. The time of its remaining on the head is one year: as the period of its fall approaches, a reddish inark of separation is observed between the process of the frontal bone and the antler. This becomes more and more distinctly marked, until the connection is entirely destroyed.

The skin of the forehead extends over the process of the frontal bone when the antler has fallen: at the period of its rege

neration, a tubercle arises from this pro cess, and takes the form of the future antler, being still covered by a prolongation of the skin. The structure of the part at this time is soft and cartilaginous; it is immediately invested by a true perios teum, containing large and numerous vessels, which penetrate the cartilage in every direction, and by the gradual depo. sition of ossific matter convert it into a perfect bone.

The vessels pass through openings in the projecting bony circle at the base of the antler: the formation of this part, proceeding in the same ratio with that of the rest, these openings are contracted, and the vessels are thereby pressed until a complete obstruction ensues. The skin and periosteum then perish, become dry, and fall off; the surface of the antler re. maining uncovered. At the stated period it falls off, to be again produced, always increasing in size.

The skeleton of quadrupeds deviates more from that of man, in the form of the lower jaw bone, than in any other part. This difference consists chiefly in the want of a prominent chin; that peculiar charac teristic of the human countenance, which exists in every race of mankind, and is found in no other instance whatever. Man has also the shortest lower jaw in compa rison with the cranium; the elephant, perhaps, approaching the nearest to him in this character. The same bone is further distinguished by the peculiar form and direction of its condyle. The articulation of these processes varies according to the structure of the masticating organs. They are both situated in the same straight horizontal line in the fere; their form is cylindrical; and they are completely locked in an elongated glenoid cavity, whose margins are so extended before and behind the condyle, that all rotatory motions are rendered impossible, and hinge like movements only allowed. This structure is most strikingly exemplified in the badger, where the cylindrical condyles are so closely embraced by the mar gins of the articular cavity, that the lower jaw (at least in the adult animal) is still retained in its situation, after the soft parts have been entirely removed by maceration. In many herbivorous ani mals (in the most extensive sense of the term) these condyles are really rounded eminences; viz. in the elephant and bea

ver.

Their surface is flattened in the pecora, which have also the lower jaw narrower than the upper, so that the two sets of teeth do not meet together when

the mouth is shut, but are brought into contact by the free lateral motion which takes place in rumination.

As the motions of the lower jaw must be materially influenced by the form of its condyles, and by the manner in which those processes are connected to the articular cavity of the temporal bone, we shall find, as might have been expected, a close relation between these circumstances and the kind of food by which an animal is nourished. Thus, the lower jaw of the carnivora can only move upwards and downwards, and is completely incapable of that horizontal motion which constitutes genuine mastication. Hence these animals cut and tear their food in a rude and coarse manner, and swallow it in large portions, which are afterwards reduced by the solvent properties of the gastric juice. Such mammalia, on the contrary, as live on vegetables, have, in addition to this motion, a power of moving the lower jaw backwards and forwards, and to either side, so as to produce a grinding effect, which is necessa ry for bruising and triturating grass, and for pulverising and comminuting grains. In all these, therefore, the form of the condyle, and of its articular cavity, allows of free motion in almost every direction. The teeth may be compared, in the former case, to scissars; in the latter, to the stones of a mill.

THE TEETH.

The jaws of the mammalia, with a very few exceptions, contain teeth. The proper whales (balana,) the pangolin (manis,) and the American ant-eaters, are the only genera entirely destitute of these organs.

Animals of the genus balana (the proper whales) have, instead of teeth, the peculiar substance called whalebone, covering the palatine surface of the upper jaw this resembles in its composition hair, horn, and such matters.

The lower surface of the upper jaw forms two inclined planes, which may be compared to the roof of a house reversed; but the two surfaces are concave. Both these are covered with plates of the whalebone, placed across the jaws, and descending vertically into the mouth. They are parallel to each other, and exist to the number of two or three hundred on each of the surfaces. They are connected to the bone by the intervention of a white ligamentous substance, from which they grow; but their opposite edge, which is turned towards the cavity of the

mouth, has its texture loosened into a kind of fringe, composed of long and slender fibres of the horny substance, which therefore covers the whole surface of the jaw. This structure probably serves the animal in retaining and confining the mollusca, which constitute its food.

The teeth of the ornithorhynchus paradoxus and hystrix deviate very considerably from those of other mammalia. In the former animal there is one on each side of the two jaws it is oblong, flattened on its surface, and consists of a horny substance adhering to the gum. There are likewise two horny processes on the back of the tongue: these point forwards,and are supposed by Mr. Home to prevent the food from passing into the fauces before it has been sufficiently masticated. In the ornithorhynchus hystrix there are six transverse rows of pointed horny processes at the back of the palate, and about twenty similar horny teeth on the corresponding part of the

tongue.

The teeth of the human subject seem to be designed for the single purpose of mastication, and hence an erroneous conclusion might be drawn, that they serve the same office in other animals. Many exceptions must, however, be made to this general rule. Some mammalia, which have teeth for the office of mastication, have others, which can only be considered as weapons of offence and defence; viz. the tusks of the elephant, hippopotamus, walrus, and manati. The large and long canine teeth of the carnivora, as the lion, tiger, dog, cat, &c. not only serve as natural weapons to the animal, but enable it to seize and hold its prey, and assist in the rude laceration which the food undergoes previous to deglutition. The seal, the porpoise, and other cetacea, as the cachalot, have all the teeth of one and the same form, and that obviously not calculated for mastication. They can only assist in securing the prey which forms the animal's food.

As the number and arrangement of the teeth was made by Linnæus the basis of his classification of animals, it may be worth while to mention, that this anatomist gives the name of primores to the front, or incisor teeth; and of laniarii to the canine or cuspidati. The term of tusks is applied to such teeth as extend out of the cavity of the mouth.

Certain classes of the teeth are entirely wanting in some orders, classes, and genera of quadrupeds; and in other instances, the different descriptions of teeth,