THE LIMBS 



155 



elongated, narrow and flat scapula, the short and ob- 

 liquely placed humerus, the consolidated radius and 

 ulna, the immensely developed middle metacarpal and 

 its digit, and the suppression of all the others. More- 

 over, all the joints from the shoulder downwards are 

 simply hinge-joints, allowing free fore-and-aft flexion 

 and extension, but scarcely any movement in any other 

 direction. 



Comparison of the Skeleton of the Hind Limb 

 of the hoese with that of man 



The pelvic differs essentially from the pectoral 

 girdle, inasmuch as it is firmly fixed to the trunk, to 

 fit it for the more important part the hind limb takes 

 in sustaining and propelling the body in walking and 

 running. Several of the vertebrae of this region are 

 united into a solid block, the sacrum, to the sides of 

 which the upper part of each arch or semigirdle is in 

 the closest contact by a large flat surface, and firmly 

 bound by strong ligaments. The arches are, moreover, 

 united to each other in the middle line below, without 

 the intervention of anything corresponding to a sternum 

 or clavicle. On the outer side of each semigirdle is a 

 deep round cup-shaped depression, the acetabulum, into 

 which the head of the first bone of the limb proper is re- 

 ceived, and which therefore corresponds with the glenoid 

 fossa of the shoulder. The joint at this position is 



