attachments the pronator quadratus of the fore limb: it is most developed in the pedimanous climbing Marsupials, where the rotation of the foot is more frequent and extensive.

Fig. 5 shows this modification of the muscles of the hind-foot in the Phalangista vulpina; a, is the expanded tendon of the sartorius; b, gracilis; c, semitendinosus; and d, semimembranosus; both these muscles are inserted, as in many other quadrupeds, low down the tibia e, gastrocnemius; f, plantaris; g, the homologue of the flexor longus pollicis pedis; h, tibialis posticus; this muscle divides and is inserted by two tendons, h' and h", into the internal and middle cuneiform bones; i, the rotator muscle of the tibia.

In the muscles on the anterior part of the leg, the extensor brevis digitorum has its origin extended into this region, and is attached to the outside of the fibula. There are three peronei; the external one is inserted into the proximal end of the fifth metatarsal: the tendon of the middle peroneus crosses the sole in a groove of the cuboid like the peroneus longus: the internal peroneus is an extensor of the outer or fifth toe. The Perameles lagotis, among the saltatorial Marsupials, presents a different condition of the extensors of the foot from that above described. The gastrocnemii, soleus, and plantaris all arise above the kneejoint, and the tendon of the plantaris, after sheathing the tendo Achillis and traversing the long sole, is finally inserted into the base of the metatarsal bone of the fourth or largest toe; thus this muscle, which is strongly developed, bends both this toe and the knee, while it extends the foot.

In the Kangaroo the flexor of the toes rises from the outer tuberosity of the tibia, its fleshy part covers the back of the leg beneath the soleus, the tendon passes to the sole and divides into a large tendon for the principal toe, fig. 211, iv, a smaller tendon for the outer toe, v, and a still smaller tendon which goes to the two slender inner toes. The muscle seems to combine the homologues of the flexor hallucis and flexor digitorum, with, perhaps, also that of the tibialis posticus.

§ 195. Muscles of Lissencephala.-The Rodentia closely resemble the Marsupialia in their muscular system; with like modifications according to the absence or presence of clavicles, and to the gradatory, saltatory, scansorial, and fossorial movements of the species respectively. They have not the marsupial modifications of the cremaster and abdominal muscles, nor the rotatory muscle of the tibia; but certain Rodents show peculiarities of the masseter which will be noticed in connection with the organs of mastication.

The Insectivora afford examples of special muscular developement in the fore part of the trunk and pectoral limbs of the Mole, fig. 6, and in the muscles which act upon the prickly skin of the Hedgehog, figs. 7 and 8.

The dermal muscles are powerful and extensive in all Insectivora: in the Mole (Talpa europæa), fig. 6, the insertion of one of these is seen at a: it assists in retracting the trowel-like

Muscles of the fore part and limbs of a Mole (Talpa europaea). XLIII.

fore limb; and, when this is the fixed point, draws forward the pelvis and thigh. The muscles of the scapula are singularly developed and modified: the trapezius operates upon the short base of the elongate bone with great advantage. The anterior portion, d, arising from the occiput, derives further strength from the ossified nuchal ligament,' and is inserted at e: the part answering to the posterior fibres of the muscle, f, arises as far back as the lumbar vertebræ to be similarly inserted into the base of the scapula, antagonising the former. The splenius capitis,' h, derives fibres from the nuchal style, as well as from certain dorsal and cervical vertebræ : it is inserted into the paroccipital region of the cranium. The sterno-mastoid, g, joined by a 'cleido-mastoid' from the cubical clavicle, is a very powerful muscle which expands to be inserted into the lateral part of the superoccipital and fascia covering the mandibular angle. The deltoid, k, coextensive with

the scapula, acts through its length with great power upon the well-developed humeral ridge. The teres major,' 1, commencing at the thickened base of the scapula, and deriving fibres from the lower facet of that triedral bone, combines to be inserted into the humerus with part of the latissimus dorsi, m; a strip from which muscle is extended to the olecranon. The triceps, o, arising from both scapula and humerus, is extremely broad and thick, calling for an extended olecranon for adequate insertion. Part of the powerful flexors of the hand (fl. digitorum, q, fl. carpi ulnaris, r), and part of the extensors, t, are shown in this view. The pectoralis consists of five thick fasciculi, four of which rise from the sternum, and one from the clavicle: they converge to be implanted into the great humeral crista pectoralis:' to these is added a fasciculus of which the homologue may be traced in Cetacea and Ungulata, passing transversely from one insertion of the pectoral to the other, and serving to combine both trowels in vigorous fossorial action. Of the muscles of the jaws the 'temporalis' is shown at b, and the masseter' at c.

The Hedgehog (Erinaceus) manoeuvres its armour of spines by means of powerfully developed and specially arranged cutaneous muscles. By putting any part of the integument on the stretch, the spines are erected, and their points held firm against the assailant by the same act of stretching the skin, the proportion

thereof to which the prickly armour is restricted can be drawn over the whole of the exposed surface of the animal, which in this act rolls and squeezes itself into the shape of a ball. In fig. 7, the Hedgehog is dissected as in the ordinary posture, or unrolled. The layer of muscle, a, a', a', consists of concentric fasciculi, thin over the middle of the back, a, and becoming thicker toward the periphery, a', a', which is well defined. All the

fibres are closely attached to the derm, and to the fibrous capsules of the roots of the spines. To the circumference of this circular muscle are attached shorter ones at right angles: a pair of these, b, arise from the caudal diapophyses, pass forward and expand to interblend with the posterior periphery: a second pair, d, with attachments to the nasal and premaxillary bones, pass backward over the forehead to the anterior periphery: a third pair, e, arising from the fore part of the sternum, pass forward and outward, diverging, and ascending in front of the shoulder to the antero-lateral part of a. A muscle, c, from fascia external to the mandibular angle, ascends between the auditory meatus and the eyeball, and combines with d in operating on the fore part of the great orbicular muscle.

8

When the Hedgehog assumes its offensively defensive position. it bends and retracts the head and draws forward the pelvis, curving the back, as in fig. 8: the converging slips b, c, d, e, pull down the orbicular muscle, which relaxes to slip over the projecting parts: the peripheral part, a', a', having descended below these, contracts, and encloses the head, limbs, and body, in an orbicular form. In resuming the normal position the sphincter relaxes, the head is rotated forward, the pelvis and tail are drawn back, the limbs begin to extend themselves: the orbicularis, a', a', is pushed up beyond the meridian, and then contracts, disposing itself, after full extension of the parts beneath, upon the dorsum of the animal, as in fig. 7. Superficial sheets of muscle, extending from the shoulder joint backward, s, and over the abdominal region, g, concur with the above-described in the motions of rolling and unrolling the animal. One of the lateral muscles of the snout is shown at m, the masseter

at c.

XLIII.

In the order Bruta the most notable modifications of the muscular system are met with in the Anteaters.

On reflecting the skin from the under part of the head in Myrmecophaga jubata, there is seen a feeble developement of a panniculus carnosus in the form of thin transverse fasciculi occurring at intervals of from two to three inches, where they underlie the rami of the slender elongated under-jaw. These muscular strips (dermogulares) have their attachments exclusively in the integument, and aid in accommodating its movements to the alternating expansion and contraction of the great gular dilatation near the base of the tongue. The transverse fasciculi are crossed by a longitudinal strip of cutaneous muscle (dermolabialis posticus) on each side of the under part of the head and neck; the strip emerges from beneath the fore part of the great subpectoral gland; it diminishes in breadth and increases in thickness as it extends forward, assuming near the mouth the character of a muscle independent of the skin, where, passing beneath the tendon of the retractor anguli oris, it is inserted into, or blends with, the fibres of an accessory portion of the orbicularis oris.

A shorter longitudinal muscular strip (dermolabialis anticus) arises from the integument below the fore part of the preceding muscle, becomes free as it advances, and is inserted into the proper orbicularis oris.

The flattened and slightly separated fasciculi of the dermoabdominalis arise from the fascia covering the anterior and inferior part of the sternum and contiguous sternal ribs; also from a median raphé of the subcutaneous fascia, attached to the linea alba, and extending two-thirds of the way towards the pubis. The anterior two-thirds of the above muscular sheet are joined by a broad layer of similar flattened fasciculi covering the side of the thorax, and the muscle so formed passes obliquely downward and outward, converging to form a thick fleshy band, about two inches broad, which is continued along the inner and upper part of the thigh, and becomes slightly twisted prior to its attachment to the aponeurosis covering the knee-joint.

The posterior portion of the dermo-abdominalis consists of thinner and more scattered flattened fasciculi which pass outward and downward, and, as they diverge from the median line, are lost in the subcutaneous fascia covering the tendinous expansion of the obliquus externus abdominis. Between the dermo-abdominalis and the proper abdominal muscles there is a moderately thick layer of elastic cellular tissue.

In the dissection of the head of the Great Anteater, three pairs of long and slender muscles are met with, which relate to the movements of the head.