290 



MARSUPIALIA. 



while the other tendon bends and prcnates; 

 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 teres, 

 which has the usual origin, insertion, and rela- 

 tive proportions, and next the palmaris longus. 



There are, likewise, distinct and strong fas- 

 ciculi of muscles corresponding to the flexor 

 carpi ulnaris and radialis, and to the flexor 

 sublimis digitorum. 



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 profundus ; 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 here con- 

 centrated upon the three long middle fingers. 



Thepronator quadratus runs the whole length 

 of the interosseous space, passing from the radius 

 a little obliquely downwards to the ulna. 



The supinator longns, 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 whole power of 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- 

 hensile faculty, are sacrificed to the acquisition of 

 force for the essential action. In no Marsupial 

 is the hand so cramped as in the Perameles, 

 excepting in the Charopits, 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 month 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 procumbent position of the trunk in 

 the Saltatorial Entomophaga. 



The muscles of the hinder extremity are 

 chiefly remarkable in the Kangaroo for their 

 prodigious strength and unusual number: the 



accessory muscle of the biceps, e. 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.f 



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 g/ut<ei are so disposed as to extend 

 the thigh, while the internal glutteus inflects 

 and rotates it inwards. 



In a Bandicoot (Perameles lagotis) the sar- 

 torius ran nearly parallel with and dermad of 

 the rcctits, 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 and vasti, removing that tendon 

 further from the centre of motion and increasing 

 the power of the extensor muscles of the leg. 



The rectu& fomoris has its two origins very 

 distinct, and its analogy to the biceps of the 

 upper extremity is very close. The gracilis 

 is a very thick and strong muscle. 



The biceps flexor cniris in the Perameles is 

 a muscle of very great strength; it terminates 

 in a strong and broad aponeurosis, which ex- 

 tends over the whole anterior part of the tibia, 

 being attached to the rotular tuberosity of that 

 bone, and terminating below in the sheath of 

 the tendo Achillis, whereby this muscle be- 

 comes an extensor of the foot. 



It is a curious fact that all the equipedal 

 Marsupials, whether burrowers as the Wom- 

 bat, climbers as the Koala, Phalangers, and 

 Opossums, or simply gressorial, as the Da- 

 sj/iirii/d-, have the tibia and fibula so connected 

 together as to allow of a certain degree of ro- 

 tation upon each other, analogous to the pro- 

 natory and supinatory movements of the bones 

 of the antibrachium, and the muscles of the 

 leg present corresponding modifications. It is 

 not without interest in the question of the 

 affinities of the Marsupials to find that none 

 of the analogous carnivorous, pedimanous, or 

 rodent Placentals present this condition of the 

 hind leg. 



In the Dusyurus niacrunis, the plantaris, 

 instead of rising from the femur, has its fixed 

 point in the fibula, from the head to half-way 

 down the bone, fleshy ; its tendon passes ob- 

 liquely inwards and glides behind the inner 

 malleolus to its insertion in the plantar fascia, 

 so that it rotates the tibia inwards besides ex- 

 tending the foot. The soleus has an extensive 

 origin from the proximal to near the distal end 

 of the fibula. There are as usual three deep- 

 seated muscles at the back of the leg. Of 

 these three the muscle analogous to the tibialis 

 post ic us is readily recognized; its tendon glides 



* Cuvier, loc. cit, p. 501. 

 t Ibid. p. 502. 



