44 FORM AND ACTION. 



the arm of a man or a monkey, hence arise such differences in 

 their structure as we might expect to find from knowing how 

 vastly unlike they are in their economy : the arm of the quadru- 

 ped, in fact, becomes a leg ; the hand, a foot ; and the offices of both 

 altogether transposed. A man has it in his power to crawl or 

 walk upon his hands and feet somewhat after the manner of a 

 quadruped ; a monkey does so by nature, at the same time that he 

 possesses the power, to a certain degree, of erecting himself and 

 walking upon two legs like a man, and using his fore limbs after 

 the manner of arms : although, however, the monkey makes use 

 of his upper or anterior extremities in this double capacity, neither 

 in progression nor manipulation is he any thing like so perfect as 

 quadrupeds on the one side and man on the other. It is the 

 set-off of the humerus from the body — its connexion with the 

 trunk by the head alone — which, with a somewhat different form- 

 ation of joint between it and the scapula, enables the bone to 

 perform all the various motions we see the arm of a man capable 

 of: whereas, confined and bound to the sides of the ribs, as we be- 

 hold it in the quadruped, it is simply susceptible of pla}dng back- 

 wards and forwards, or, at least, of very little other kind of motion. 

 The scapula, being abroad flat bone, presents two large surfaces; 

 an inner one, which is uniform and smooth, and a little excavated 

 in order to adapt it the better to the convexities of the arches 

 of the ribs, against which it is applied ; and an outer one, having a 

 longitudinal ridge {Fig. Ill, 2, 3) running upon it, unequally dividing 

 it into two smaller surfaces. Between the scapula and the ribs there 

 is no joint — neither osseous nor ligamentary connexion, but only 

 a fleshy one : muscles alone attach the shoulders to the body ; and 

 as the body is supported anteriorly by the fore limbs, it follows 

 that thus much of the weight is borne by muscular action, or, at 

 least, by muscles becomes transmitted to the legs or pillars of sup- 

 port. A man by passing a knife between the scapula and the 

 ribs would easily sever these fleshy attachments, and in this man- 

 ner let fall the fore part of the trunk, and the head and neck along 

 with it, to the ground. This constitutes the essential difference 

 in their relations with the body between the fore and hind extre- 

 mities : while the latter are connected to the trunk and support 

 the hind parts of it through the medium of joints, the former hold 



