THE MAMMALIA— MAN AND BEASTS. 



91 



rated from it. Caustic alkalis and some acids dissolve it entirely. Sulphur, silica, 

 iron, and manganese, may be traced in the hair. 



There are certain prolongations of a horny substance, which grow upon the heads 

 of some species of Mammalia, especially the Ruminantia. These also appear on 

 seTeral other parts of animals. 



The term Horn, as applied in the arts, would esclude the excrescences of the Stag, 

 Deer, Rein-deer, Elk, and others, which consist rather of a bony substance, distin- 

 guished by the term antlev. The horns of this division of Ruminants are true bones, 

 and composed like thcra of a cartilaginous matter, within the meshes of which, par- 

 ticles of phosphate of lime are deposited, constituting a kind of earthy salt, commonly 

 known as earth of bones or hartshorn. 



These antlers, in their perfect state, are true bones both in their texture and ele- 

 ments, the external part being hard, compact, and fibrous ; the internal spongy, but 

 very solid- There are no large cells, medullary cavities, or sinuses. The bases of 

 these antlers adhere to the frontal bone, forming one body with it, in such a way as 

 to render it impossible to point out, at certain ages, the limits between them. The 

 skin which covers the forehead does not extend farther. It is surrounded by a den- 

 ticulated bony substance, called the burr. Neither skin nor periosteum covers this 

 substance or the rest of the antler. Furrows more or less deep, which are the ves- 

 tiges of vessels distributed along their surfaces while they were yet soft, are alone 

 to be traced on the exterior. These hard and naked horns remain only for one year 

 on the head of the Stag. The period of their fall is varied according to the species; 

 but when near, there appears, on sawing them longitudinally, a reddish mark of 

 separation between them and the supporting eminence of the frontal bone. This 

 mark becomes gradually more apparent, and the bony particles at length lose their 

 adhesion at that part. A very slight shock then makes the antlers drop off at that 

 period, and two or three days commonly intervene between the fall of the one antler 

 and that of the other. 



The eminence of the frontal bone resembles, at that time, a bone broken or sawed 

 through transversely, and its spongy texture is exposed. The skin of the forehead 

 soon, however, covers it ; and when the horns are again about to shoot, tubercles 

 arise, which remain covered by a production of the same skin until their perfect size 

 has been attained. During the whole of this operation, the tubercles are soft and 

 cartilaginous. Under the skin a true periosteum is found, in which vessels, some- 

 times of great size, are distributed, and penetrate the mass of cartilage in every 

 direction. The cartilage ossifies gradually, and, passing through the same stages 

 as the bones of the fcetus, ends in becoming a perfect bone. During this time, 

 the burr at the base of the horn penetrates the indentations through which the 

 vessels pass, and also develops itself. The indentations by their growth confine the 

 vessels, and finally obstruct them. Then the skin and periosteum of the bones wither, 

 die, and fall off. The bones, now become bare, in a short time fall off, only to be 

 renewed by others, but always of a larger size than the first. The antlers of the 

 Stag are subject to diseases equally with other bones, and of the same kind. In 

 some the calcareous matter is extravasated, and forms different exostoses ; in others, 

 on the contrary, it is found m too small a quantity, and the bones continue porous, 

 light, and without consistence. 



The true horns, such as those of the Bull, Ram, Goat, and Chamois, are formed 

 upon processes of bone, and differ materially from antlers in this respect, that they 

 grow at their root or base, and bear a great analogy to the other integuments. 



This view is established by investigating the manner in which the horns of the 

 Calf exhibit themselves. In the third month of conception, while the fcetus of the 

 Cow is still inclosed in the membrane, the cartilaginous frontal bone presents no 

 mark of the horns which it afterwards bears. It becomes partly ossified towards the 

 ■seventh month, and presents in its two portions the small tubercle, which appears to 

 be produced by the elevation of the osseous lamina;. These bony tumours soon after 

 appear externally, and raise the skin in proportion as the tumour grows. At last it 

 becomes horny as it elongates, and forms a kind of sheath which covers externally 

 the process of the frontal bone. There are numerous branches of blood-vessels, 

 which serve to nourish the bony part, and are placed between this sheath and the 

 frontal bone. 



Thus, the horns are merely solid, hard, elastic, and insensible sheaths, which pro- 

 tect the osseous prolongation of the frontal bone. These sheaths, generally of a 

 conical figure, are broadest at the base, or extremity from which they grow. The 

 curvatures assumed by the horns axe different in the several species ; they also pre- 

 sent different channels or transverse furrows, depending on the age of the animal ; 

 and these denote, in a very certain manner according to the species, the number of 

 years it has lived. The horns grow in precisely the same manner as the nails of 

 animals and the beaks of birds ; that is to say, from the bone which serves as a base 

 there exudes a gelatinous matter, which takes the form of the horn, and hardens on 

 cominf in contact with the air. M. Vauquelin has found this gluten, or animal 

 mucus, to be of precisely the same chemical nature as that found in hair. 



The texture of the horns appears to be much the same in the Ram, Goat, Ante- 

 lope, and Bull. They consist of fibres of a substance very analogous to hair, and 

 appear to be agglutinated in a very solid manner. These fibres in the two genera 

 first mentioned are short, and covered by superincumbent layers like the tiles of a 

 house. In the last two they are longer, more compact, and form elongated cones, 

 the one being incased within the other. 



It appears that the horns of the Rhinoceros differ materially from those of the 

 Ruminantia. They have no osseous part, and are not placed upon the frontal bone, 

 but upon the ridge of the nose. They are formed, however, of the same substance, 

 and we observe fibres analogous to hairs more distinctly in this animal than perhaps 

 in any other. The base of the horn presents externally an infinite number of rigid 

 hairs, which seem to separate from the raa-^s, and render that part rough, like a 

 brush, to the touch. "^Iien sawed transversely, and examined with a magnifying 

 glass, we perceive a multitude of pores, seeming to indicate the intervals resulting 

 from the union of the agglutinated hairs. When divided longitudinally, there are 

 numerous parallel and longitudinal furrows, which demonstrate a similar structure. 

 This kind of horn is attached solely to the skin. The horns of the Two-horned 



Rhinoceros ( Rhinoceros hicornis) always appear in some degree moveable. When 

 fixed, as in the Indian Rhinoceros {R, Indicus)^ there is a thick mucus interposed 

 between its base and the bone over which it is situate. 



The whale-bone, which lines the interior of the upper jaw in the Whales, also 

 consists of hair united into larainse. 



The colour of horns depends, like that of the hairs, on the colour of their mucous 

 tissue. Heat softens bone, and even fuses it ; hence this agent is largely employed 

 in manufacturing them into different articles. 



It appears from these observations, that true horns differ essentially from the bony 

 prolongations called antlers in the Deer. The latter increase at their extremity, 

 and are covered with skin during their growth. They fall off when their growth is 

 completed, and are replaced by others. The true horns are developed at the base, 

 are covered with skin, and remain permanently. 



The Nails of the iVIammalia form, with the preceding, useful arms of attack, or 

 necessary shields against external injury. These horny prolongations are generally 

 equal in number to that of the fingers and toes, whose extremities they serve to arm 

 and protect. Their form depends upon that of the last phalanx of each finger or toe, 

 and they bear the same relation to these phalanges, as the hollow horns to the pro- 

 cesses of the frontal bone which they cover. 



The nails seem to be incased in a fold of the skin, the portion covered by the 

 latter being called the root of the nail. They grow by this part precisely in the 

 same manner as hairs, but the opposite extremity wears away by friction, from the 

 various uses to which animals apply their nails. Accordingly, they are observed to 

 grow exceedingly long in animals that are confined, and have few opportunities of 

 motion. No part of a nail is sensible, except that which adheres to the skin, and 

 the free extremity may be cut or broken without occasioning the slightest pain. 

 The colour of the naUs depends upon that of the mucous tissue. 



The human nails appear in the third month of conception ; and their development 

 takes place nearly in the same manner as in the common horns. They appear at first 

 Uke a kind of cartilage, which gradually acquires a proper consistency. Almost all 

 animals have the nails formed, in some degree, at the time of their birth. The 

 nails of Man, as well as the greater part of the Unguiculated Mammalia, appear to 

 be formed of extremely thin layers, placed one upon another. The external laminai 

 are larger than those of the inferior surface ; on which account we do not readily 

 perceive tliis kind of imbrication which actually takes place. When diseased, how- 

 ever, or upon making a transverse section of the nail, after it has become completely 

 dried, this structure becomes evident. Often we observe stria?, or very fine longi- 

 tudinal and parallel lines, appar*^ntly resulting from the manner in which this part is 

 moulded upon the laminsc beneath it. 



Nails are generally wanting in animals which do not employ their extremities 

 either in walking or grasping, as we may remark in the Cetacea. When analyzed 

 chemically, the nails afford nearly the same results as hair, to which they bear con- 

 siderable analogy, both in structure and their mode of growth. 



Hoofs surround the phalanx entirely, in which respect they differ completely from 

 nails. They are neither pointed nor cutting at the extremity, and both surfaces 

 meet to form a round and blunt edge. Their interior is rendered remarkable by 

 deep iind regular furrows, which receive projecting lamina not observable in nails. 

 In tho Elephant and Rhinoceros these furrows are very strongly marked. They 

 are a.so conspicuous in the Horse, but do not appear very prominently in the Ru- 

 minantia. A layer of mucous matter may always be observed between the nails and 

 the soft parts of the phalanx. In hoofs there is found a soft substance abounding in 

 nerves, which serve to maintain a certain degree of sensibility in these parts. 



Scales may be regarded as very flat horns, in the same way as hairs admit of being 

 considered very slender horns. They bear a great resemblance to hairs, feathers, 

 boms, and nails, both in their mode of growth and use, as well as in respect to their 

 chemical analysis. Only a very few species of MammaUa possess scales on some 

 parts of their body, and in Birds they are found on the feet alone. Reptdes and 

 Fishes are, on the contrary, almost wholly covered by them. 



The terra scales is applied to a variety of substances of very different natures. 

 In general, they consist of laminse or small plates of a substance which may either 

 be horny or bony. The scales of the animals belonging to the Genus Manis consist 

 of a kind of flat nails of a horny substance, but of considerable thickness ; their an- 

 terior third, which is bevelled and sharp edged, is free, while they adhere to the skin 

 by the other portion. The external surface is channelled longitudinally, particularly 

 in the Long-tailed Manis (Manis tetradactyla), in which animal they usually termi- 

 nate in three points. They are furrowed transversely on the side next the skin, and 

 appear to be formed of imbricated laminae. In the Armadilloes, the scales consist of 

 small compartments of a calcareous substance, covered with a thick, smooth, and ap- 

 pai-ently varnished epidermis. The scales covering the tail of the Beaver consist 

 of thin laminae of a horny substance, similar to those on the feet of Birds. The 

 tails of Rats, Opossums, and most animals with prehensile tails, are covered with 

 scales of the same nature. 



GENEEAL EEVIEW OF THE MAMMALIA CONTINUED. 

 Their Organs of Voice. 

 Man alone of all Mammalia possesses the exclusive privilege of uttering articulate 

 sounds, to which the great flexibility of his tongue and lips, as well as the general 

 form of his mouth, alike contribute. The power of communicating his ideas by arti- 

 ficial words, forms a means of communication of the greatest value ; and there are 

 no signs capable of being employed with the same convenience for this purpose, or 

 which could be perceptible at so great a distance, or in so many directions. This 

 faculty of speech, joined to the perfection of the hand in Man, contributes largely to 

 his power. 



The other Mammalia can express their wishes by cries alone ; yet these natural 

 signs are themselves subject to many modifications. Although incapable of commu- 

 nicating any coroplicat-d idea, they at least serve to express the passions by which 



