MUSCULAR SYSTEM OF MAMMALIA. 13 



itself into two distinct pemiiform muscles ; the tendon of the 

 outer one joins that of the brachialis, and this conjoined tendon 

 simply bends the fore-arm, while the inner tendon bends and pro- 

 nates ; the latter, which is a direct though partial continuation of 

 the biceps, is inserted into the ordinary tubercle of the radius ; 

 whereas the outer tendon is attached to the fore part of the proxi- 

 mal 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 relative proportions, and next a large pal- 

 inaris longus. There are, likewise distinct and strong fasciculi of 

 muscles corresponding to tia&Jlexores carpi ulnaris and radialis, and 

 to thejferor sublimis diyitorum. The strong ridge continued from 

 the olecranon to the posterior and inner part of the ulna gives 

 origin to a great proportion of the oblique fibres of the flexor pro- 

 fundus ; but both this and thejflexor sublimis terminate in a single 

 thick and strong tendon, which after passing the wrist divides into 

 those corresponding with the perforating and perforated tendons 

 concentrated, in Perameles, upon the three long middle fingers. 

 The pronator quadratics runs the whole length of the interosseous 

 space, passing from the radius a little obliquely downward to the 

 ulna. The supinator longus, 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 by the other 

 into the adjoining metacarpal bone. 



These are the principal muscles of the fore extremity which 

 require notice. 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 ; the whole power of the deep and superficial 

 flexors is concentrated upon the fossorial and well-armed fingers ; 



and, by the sinoie common tendon in which the fleshy fibres of 



j ~ > 



these muscles terminate, they move them collectively and simul- 

 taneously. 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 Chceropus, where the functional 

 and fossorial fingers are reduced from three to two. It is in rela- 



o 



tion to this condition, doubtless, that the clavicles are wanting in 

 these genera, while all other Marsupials possess them. In these 



