The biceps is a powerful muscle, although its short head from the coracoid process is sup pressed. The long head has the usual origin and relation to the shoulder-joint ; its tendon is very thick and short. The fleshy belly joins that of the strong brachialis internus, situated at the external side of the humerus, whence it takes its principal origin from the short deltoid ridge, closely connected there with the second portion of the triceps, and deriving some fleshy fibres from the lower and outer third of the humerus. The portion of the biceps arising by the long head soon resolves itself into two distinct penniform muscles ; the tendon of the outer one joins that of the brachialis, and this conjoined tendon simply bends the fore-arm, while the other tendon bends and pronates; this, which is a direct though partial continua tion of the biceps, is inserted into the ordinary tubercle of the radius ; whereas the other ten don is attached to the fore part of the proximal end of the ulna.
The muscles which arise from the internal condyle of the humerus are the pronator Peres, which has the usual origin, insertion, and rela tive proportions, and next the palmuris longus.
There are, likewise, distinct and strong fas ciculi of muscles corresponding to the flexor carpi ulnaris and raffia/is, and to the flexor sublimis digitornm.
The strong ridge continued from the olecra non to the posterior and inner part of the ulna gives origin to a great proportion of the oblique fibres of the flexor prifondus; but both this and the flexor sublimis terminate in a single thick and strong tendon, which after passing the wrist divides into those corresponding with the perforating and perforated tendons liere con centrated upon the three long middle fingers.
The prom for guadratus runs the whole length of the interosseous space, passing from the radius a little obliquely downwards to the ulna.
The supinator Imigus, arising as usual from the upper part of the strongly developed ridge above the outer condyle, sends its tendon across the carpal joint, which tendon divides before it crosses, and is inserted by one of its divisions into the base of one of the metacarpal bones of the index finger, and the other to the adjoin ing metacarpal bone.
These are the principal muscles of the fore extremity which require notice in this place. Their modifications, in respect of number and strength, relate to the act of digging up the soil, which is habitual in the Bandicoots, as it is for the purpose of obtaining food, and not for shelter. It is for this purpose that the three
middle digits of the hand are developed at the expense of the other two, which are rudimental ; and we have seen that the whol e powerof the deep and superficial flexors is concentrated upon the fossorial and well-armed fingers; and that by the single common tendon in which the fleshy fibres of these muscles terminate, they move them collectively and simultaneously. Thus variety of application, and especially the pre hensilefaculty, are sacrificed to theacquisition of force for the essential action. In no Marsupial is the hand so cramped as in the Perameles, excepting in the Cheropus, where the functional and fossorial fingers are reduced from three to two. It is in relation to this condition, doubt less, that the clavicles are wanting in these genera, while all other Marsupials possess them. The inverted position of the pouch in the Pera meles might also be conceived to have relation to their imperfect hands, the mouth of the pouch being thus brought nearer to the vulva ; but I am disposed to regard it as being more essentially connected with the habitually in clined or procumbeut position of the trunk in the Saltatorial Entomopliaga.
The muscles of the hinder_ extremity are chiefly remarkable in the Kangaroo for their rrodi6ious strength and unusual number: the accessory muscle of the biceps, o. g. is divided into two strong fasciculi, which unite to be inserted into the side of the patella;* the py riformis is also a double muscle.t The sartorius has its insertion so modified that it becomes an extensor instead of a flexor of the tibia : it is chiefly fixed to the tibial side of the patella, and by fascia into the capsular ligament of the knee-joint and the anterior proximal tuberosity of the tibia. In a Dasyure (Das. macrurus) I found that the sartorius had a similar disposition and office. In this ambulatory carnivorous Marsupial the external and middle glutei are so disposed as to extend the thigh, while the internal gluteus inflects and rotates it inwards.
In a Bandicoot (Pernmeles lagotis)the sar torius ran nearly parallel with and dermad of the reetus, and was inserted into the upper part of the patella. Besides this sesamoid, which is rarely developed in other Marsupials, I found a thick cartilage attached to its upper part and interposed between the common ten don of the recti arid vasti, removing that tendon further from the centre of motion and increasing the power of the extensor muscles of the leg.