crista of the os innominatum, and together with the sternum cover a large share of the abdomen, and support its viscera more effectually in the horizontal position of the trunk. For the same purpose too, the ribs in many cases are more numerous than in man; viz., thirty-two in the hyena, thirty-six in the horse, forty in the elephant, and forty-six in the unau (Bradypus didactylus.)

These, with other points, which cannot escape observation, when the skeleton of any rather long-legged quadruped is compared to that of man, show how unfit he is for the attitude on all fours, which in his case can never be otherwise than unsteady, irksome, and fatiguing in the highest degree.

The spine of man presents some important peculiarities resulting from his characteristic attitude. One of these is its very remarkable increase of size in the lumbar region; an augmentation corresponding to that of the superincumbent weight, and to the magnitude of the efforts which this part has to sustain. The immense bulk of the sacrum,* far exceeding, in proportion to the rest of the body, that of any animal, is referable to the same cause, to the mode in which this weight is transmitted to the hip-bones, and thence to the lower limbs, and to the peculiar construction of the pelvis. The waving line of the column, arising from a series of alternate curves in opposite directions, is altogether peculiar to man; it allows a proper distribution of the weight with respect to the centre of gravity, the line of which carried through the entire trunk must fall within the space covered by the feet, or by one foot when we support the body on one only. As this line passes through all the curves, motion is allowed in the upper regions without impairing the general equilibrium.

The cervical vertebræ of the monkeys, including the satyrus and troglodytes,§ are remarkable for the length and prominence

In the chimpansé, says Tyson, "the os sacrum was nothing so dilated and spread, as 'tis in man; but contracted and narrow, as 'tis in apes; and very remarkably different from the human skeleton." P. 69.

This is excellently represented in Albinus's plates of the skeleton; particularly in the side view, tab. iii. I refer to the original Leyden edition of this incomparable work; which, when the plates of the bones are added, constitutes the most accurate, useful, and splendid publication ever produced in anatomy. Its merits cannot be estimated from the English editions.

"Les vertèbres cervicales sont remarquables par la longueur extraordinaire des apophyses epineuses des six inférieures; mais surtout par celle du milieu." Les apophyses paroissent avoir besoin de cette longueur dans l'orang, pour qu'il puisse tenir mieux sa tête en equilibre. Je ne connois aucun autre animal dont les apophyses epineuses des vertèbres cervicales soient aussi longues, excepté le philandre d'Amérique." Camper, Œuvres, 1. 126. pl. 2. fig. 3,

Tyson, p. 68.

of the spinous processes; a peculiarity probably connected with the support of the head, which preponderates in front in consequence of the elongation of the jaws and the retreat of the occipital condyles, backwards.*

I have explained how the lower extremities afford a sufficient base of support and solid columns to sustain the trunk, and how the same point is secured by the organic arrangements of the latter. The breadth of the human pelvis forms an ample basis for the body, and a firm point of action for the abdominal and other muscles, enabling them quickly to rectify the position of the parts above. In all the digitated animals, the pelvis is so narrow, that the trunk resembles an inverted pyramid: there would be great difficulty in maintaining it in equilibrio, even if it were possible for the animal to assume the erect position. In those instances, where the pelvis is broader, as in the hoofed animals, the other conditions of the upright stature are absent. The bear, however, forms an exception to these observations, and may be taught to stand and walk erect, although the posture is manifestly irksome to the animal. When quadrupeds endeavour to support themselves on the hind extremities, as for the purpose of seizing any objects with the fore-feet, they rather sit down than assume the erect position; for they rest on the thighs, as well as on the feet, and this can only be done, where the forepart of the body is small, as in the simiæ, squirrel, &c. In other cases the animal is obliged to support itself by the fore-feet also, as in the dog, cat, &c.

CHAPTER III.

On the upper Extremities: Advantageous Construction of the Human Hand: Man is two-handed, the Monkey kind four-handed: on the natural Attitude and Gait of Monkeys.

A CURSORY survey of the upper limbs will be sufficient to convince us that they are entirely unsuited to the office of supporting the body, and as well calculated for the uses to which we put them, of seizing and holding objects, and thereby executing, besides all the processes of the arts, a thousand minute but most serviceable actions of constant recurrence.

There is a general resemblance of form throughout the upper and lower extremities: their principal divisions, the number and

* This_great_development of the cervical spines is most remarkable in the pongo, where the enormous bulk of the jaws corresponds to it. See Audebert, Hist, Nat. des Singes et Makis, fol. Planche Anatomique 2, fig. 5.

form of the bones, and the construction of the articulations in each division, correspond very clearly; the essential varieties may all be referred to the principles of solidity and resistance in the lower, of mobility in the upper, as leading purposes of the formation. A comparison of the arm, fore-arm, and hand, to the thigh, leg, and foot; of the os innominatum to the scapula; of the hip, knee, and ankle, to the shoulder, elbow, and wrist; of the carpus, metacarpus, and fingers, to the tarsus, metatarsus, and toes; will at once prove and illustrate this difference.

The scapula, placed at the posterior and lateral aspects of the trunk, are kept wide apart by the clavicles: a line falling perpendicularly from the shoulder, in the erect attitude of the body, would pass far behind the hip: thus the upper limbs are thrown outwards and backwards, and have a free range in their principal motions, which are in the anterior direction. The glenoid cavities look outwards. The arms are widely separated above, and they diverge towards their opposite ends: the lower limbs, on the contrary, converge from above downwards. In true quadrupeds, the clavicles are suppressed; * the shoulder-blades brought forwards on the chest, and approximated to each other; and the glenoid cavities are directed downwards. Consequently, the anterior or pectoral members fall perpendicularly under the front of the chest, and come still nearer together below than above.

The deep cup of the os innominatum, and the powerful orbicular ligament of the hip, are strongly contrasted with the shallow glenoid cavity and weak capsule of the shoulder: the difference between the broad articular surfaces and very powerful ligaments of the knee, and the strong joint of the ankle on one side, and the articulations of the elbow and wrist on the other, is equally striking.

The leg and fore-arm resemble each other less than the thigh and arm; in the fore-arm the parts are arranged favourably to mobility; in the leg, the object is to procure a firm and solid

It is stated, in the Physiological Lectures, p. 123, that "no animal, except the monkey, has a clavicle like that of man.' Certainly none, without excepting even the monkey, have either clavicles, or any other bones, exactly resembling the human in all points; but many, even of the more common kinds, have clavicles equal to those of man in relative size and length, as well as in office. As the use of this bone is to maintain the shoulder at its proper distance from the front of the trunk, and to prevent the scapula in particular from coming forwards on the chest, it exists in all cases, where the pectoral members are employed, either principally, or in great part, in executing purposes foreign to support, such as holding objects, climbing, flying, digging, raking the ground. It will be sufficient to mention that the lemurs and bats, the squirrel, beaver, rat, porcupine, mole, ant-eater, hedgehog, shrew, and sloth, possess perfect clavicles.

support, which can transport the centre of gravity with ease and safety from one point to another. Of the two bones of the forearm, which are nearly equal in every respect, one rolls easily over the other, and the hand is articulated with the moveable bone. In the lower extremity these rolling motions would have introduced dangerous unsteadiness and insecurity. The foot therefore is articulated with the tibia, which corresponds to the ulna; and the fibula possesses no perceptible power of motion.

The principal differences in the hand and foot occur in the relation which the carpus and metacarpus, the tarsus and metatarsus-the solid or resisting portions-bear respectfully to the phalanges of the fingers and toes, the flexible portions of the members. The solid part of the hand is less developed, and has far less volume than the analogous part of the foot, on which the whole weight of the body in standing finally rests: the phalanges, on the contrary, which are the principal agents in executing the functions of the hand, are much longer and stronger than those of the toes, which are not so essential to station or progression. The three phalanges of the middle finger equal in length the length of the carpus and metacarpus together; while the respective proportions of the tarsus and metatarsus and toes are about & and . The parts of the foot and hand are disposed inversely in respect to their importance. The posterior portion of the former, and the anterior of the latter, are of the most consequence, and possess the most remarkable characters. The functions of the hand render it necessary that its plane should be nearly continuous with that of the fore-arm ; otherwise the radius could not guide it so precisely to the objects in view. In the foot, the articulation is so disposed, that its posterior part offers a powerful lever for muscular agents, and a solid support for the mass above: it is formed by a single bone of the foot, which adds to its solidity. The metacarpus and metatarsus have a much greater similarity to each other; the latter is the more solid, and offers this principal difference. The metatarsal bone of the great toe, by far the strongest of the whole, has scarcely any motion on the tarsus, and is parallel to the others; while the corresponding bone of the thumb has a very considerable extent of motion, and is anterior to the rest of the metacarpus, supposing the palm to be turned directly forwards. These remarkable differences are easily understood, when we consider that the great toe as one of the points on which the body is supported, requires solidity; while the thumb,

being concerned in all the numerous and varied motions of the hand, must be organized for mobility.

The human hands being terminated by long and flexible members, of which only a small portion is covered by the flat nails, while the rest is furnished with a highly organized and very sensible integument, form admirable organs of touch and instruments of prehension. The animal kingdom exhibits no corresponding part so advantageously constructed in these respects. At the same time, the lateral attachment of the arms to the trunk, and the erect attitude, gives us the freest use of these admirable instruments. So greatly does man excel animals in the conformation of the hands, that ANAXAGORAS asserted what HELVETIUS has again brought forwards in our times, "that man is the wisest of animals, because he possesses hands." In such a view we can by no means coincide; yet ARISTOTLE is well justified in observing that man alone possesses hands really deserving that name. Several mammalia have also hands, but much less complete, and less serviceable than that of the human subject, which, in comparison to them, was justly enough termed by the Stagyrite the organ of all organs. The great superiority of the human hand arises from the size and strength of the thumb, which can be brought into a state of opposition to the fingers, and is hence of the greatest use in enabling us to grasp spherical bodies, and take up any object in the hand, in giving a firm hold on whatever we seize, in executing all the mechanical processes of the arts, in writing, drawing, cutting, in short, in a thousand offices, which occur every moment of our lives, and which either could not be accomplished at all, if the thumb were absent, or would require the concurrence of both hands, instead of being done by one only. Hence it has been justly described by ALBINUS as a second hand, manus parva majori adjutrix."*

66

All the simiæ possess hands; but the most distinguishing part, the thumb, is slender, short, and weak, even in the most anthropo-morphous :† regarded as an imitation of the human structure, it would almost justify the term applied to it by EUSTACHIUS, ridiculous. The other fingers are elongated and slender. +

De Sceleto, p. 465.

The thumb of the orang-outang and chimpansé, besides being much smaller than the fingers, reaches only to the metacarpo-digital joint. Camper, Euvres, pl. 2, fig. 5. F. Cuvier in the Annales du Muséum, t. 16, p. 4. Tyson, p. 12, fig. 5.

Simiæ in general have nine bones in the carpus; and Camper found the