The bar or bridge of bone (zygomatic arch) which spans across the muscle, bends strongly outwards to augment the space for its passage ; and as it gives origin to another power ful biting muscle (masseter), the arch is also bent upwards to form the stronger point of resistance during the gripe of that muscle. From almost all the periphery of the back surface of the skull there is a strong pitted ridge, affording extensive attachment to powerful muscles which raise the head, together with the animal's body which the lion may have seized with his jaws ; this beast of prey being able to drag along the car case of a buffalo, and with ease to raise and bear off the body of a man. If we next examine the framework of the fore limb, which is associated with the above-defined structure of the skull, we find that the fore paw consists of five digits (1-s) ; the innermost and shortest (I) answering to our thumb, and having two bones ; the other four digits having each three bones or "phalanges." All those digits enjoy a certain free dom of motion and power of reciprocal approximation for grasping ; but their chief feature is the modification of the terminal phalanx, which is enlarged, compressed, subtriangular, and more or less bent ; with a plate of bone, as it were, re flected forwards from the base, from which the pointed termi nation of the phalanx projects like a peg from a sheath. A powerful, compressed, incurved, sharp-pointed, hard, horny claw is fixed upon that peg, its base being firmly wedged into the interspace between the peg and the sheath. The toe-joint so armed is retractile. This complex, prehensile, and destruc tive paw is articulated to the two bones of the fore leg (m dins, n, and ulna, u) ; they are both strong, are both distinct, are firmly articulated to the arm-bone (h.) by a joint, which, although well knit, allows great extent and freedom of motion in bending and extension ; and, besides this, the two bones are reciprocally joined so as to rotate on each other, or rather the radius upon the ulna, carrying with it, by the greater expansion of its lower end, the whole paw, which can thus be turned " prone" or " supine ;" whereby its application as an instrument for seizing and tearing is greatly advantaged. The humerus or arm-bone (h) is remarkable for the extension of strong ridges from the outer and inner sides, just above the elbow-joint. These ridges indicate the size and force of the supinator, pronator, flexor, and extensor muscles of the paw. To defend the main artery of the fore leg from compression during the action of these muscles, a bridge of bone (a) spans across it as it passes near their origin. The upper end of the arm-bone is equally well marked by powerful ridges for mus cular implantation, especially for the deltoid ; but these ridges do not project beyond the round " head" of the bone, so as to impede its movements in the socket.
The blade-bone (scapula 8) is of great breadth, with well developed processes (spine, acromion, and coracoid) for mus cular attachments ; the size and shape of this bone relate closely to the volume of the muscles which operate upon the arm-bone and fore limb. A small clavicular bone (b) is inter posed between a muscle of the head and one of the arm, giving additional force and determination of action recipro cally to both muscles.
Such are some of the modifications of the teeth and frame work of a beast of prey, which concur, and were deemed by Cuvier to be correlated, in the organization of such animals.
Let us compare them with those of the corresponding parts in an ox (fig. 129). The teeth answering to the great
laniaries in the lion are absent ; at most, one recognizes the homologues of the lower canines, reduced in size and altered in shape, so as to form the outer teeth (c) of a bent row of incisors terminating the lower jaw. The back teeth (h) instead of being trenchant, have broad and flat crowns, roughened with hard ridges, opposing each other with a grinding action, like mill stones. The lower jaw is long and slender ; it articulates to the skull by a flat condyle (d), admitting of rotatory move ments upon a flattened arti cular surface on the skull, and limiting the extent of opening and shutting the mouth. The coronoid process (r) is very slender, and the fossa which marks the size of the temporal muscle (t) is correspondingly small. The zygomatic arch (o) is short and feeble, and its span is narrow ; it is almost straight, or with a slight bend downwards. The parts of the skull (pterygoid plates) which afford attachment to the rotat ing muscles of the jaw, and the (angular) part (f) of the jaw into which they are in serted, are of great extent.
The ox masticates grass with great efficiency ; it inflicts no injury to other animals with its teeth. The horns are its weapons, and they are chiefly defensive.
The fore foot of the ox is reduced to two principal toes, with two rudimentary ones dangling behind. Each of these has its extremity enveloped by a thick horny case, or hoof ; this modification is accompanied by a junction or coalescence of the radius (n) and ulna (u), preventing reciprocal rotation or movement of those bones on each other ; by a joint restricting the movement of the fore arm (antibrachium) upon the arm (brachium or humerus, h) to one plane ; by a long and narrow blade-bone (s), with a stunted coracoid and no clavicle ; in short, by modifications adapting the limb to perform the movements required for locomotion, and almost restricting it to such. This type of fore limb is always associated with broad grinding teeth, and with the modifications of jaw and skull above defined. The due amount of observation assured envier that these several modifications, like the contrasted ones in the Carnivore, were correlated, and he enumerates the physio logical grounds of that correlation.
These grounds may be traced to a certain degree in the secondary modifications of the carnivorous order. If the retractibility of the claw be suppressed, the carnassiality of the teeth is reciprocally modified. If the ungniculate foot is reduced from the digitigrade to the plantigrade type, the dentition is still more altered, and made more subservient to a mixed diet.
By the application of the correlative principle to the fossil mammalian remains of pliocene and later deposits, the have been distinguished from the Carnivore ; and out of the latter have been reconstructed extinct species of the feline, viverrine, ursine, and other families of the order. In England and continental Europe a peculiarly destructive feline quadruped existed, with the upper canines much gated, trenchant, sharp-pointed, sabre-shaped, whence the name Machairodus proposed for this feline sub-genus. It was represented by species as large as a lion (M. caltriden.s and if. laticlens); and by others of the size of a leopard (M. pal midens and M. megantereon). This form is first found in the niiocene of Auvergne and of Eppelsheim ; next in the plio cene of the Val d'Arno ; and finally in cave breccia in Devonshire.