78 THE BONES. 



perfect pentadactylous type. The carpus is composed of eight bones, the 

 metacarpus of five small, parallel, bony columns ; the phalangeal region of five 

 digits thumb, index, medius, annularis, and auricularis, formed each of three 

 phalanges, with the exception of the thumb, which has only two. 



In the domesticated animals, the constitution of the hand is more or less 

 removed from this type, in consequence of abortive development, which 

 diminishes either the number of rays, or the number of pieces composing 

 these. 



Thus, in the Cat and Pig there are eight bones in the carpus ; but in the 

 Dog and Horse there are no more than seven ; in the Ox and Sheep there are 

 only six, for in them two or three bones are fused together. 



The metacarpus of the Dog and Cat has certainly five metacarpal bones, 

 but the metacarpus of the Pig has no more than four, that of the Horse three, 

 and that of Ruminants only two. In the metacarpus of the Pig the fifth bone 

 is not developed. In the Horse it is entirely absent ; the fourth and first are 

 independent, and the third and second are confounded to form a voluminous 

 bone which has been named the principal (or large) metacarpal. In Ruminants, 

 the fourth and fifth metacarpals are quite imperfect, the first being arrested 

 in its development, and the second and third becoming consolidated as in 

 the horse. 



Lastly, it is noted that the digital region of Carnivora has five digits, 

 the Pig four, Ruminants two, and Solipeds only one. In the Pig, the thumb 

 is undeveloped; in ruminants it is completely absent, and the first and 

 fourth are represented by two small bones situated behind the metacarpo- 

 phalangeal articulation ; while in solipeds the single digit already mentioned 

 results from the fusion of the auricularis and medius. 



From this preliminary synthetical exposition, it will be easy to 

 understand the description of the bones composing the hand in solipeds. 



1. Carpal Bones. 



The carpus forms the base of the hand. Situated between the inferior 

 extremity of the radius and the superior extremity of the metacarpal bones, 

 it is composed of several small bones joined to each other in the fresh state 

 by extremely solid articular bands. Collectively, they form an almost 

 quadrilateral mass in which may be distinguished two faces and four 

 borders. 



The anterior face is slightly convex from side to side and irregular ; it 

 corresponds to the tendons of the extensor muscles of the metacarpus and 



The posterior face is very unequal and converted, especially outwardly, 

 into a groove in which the tendons of the flexor muscles of the phalanges 

 glide. 



The superior border articulates with the radius ; the inferior border with 

 the metacarpal bones. 



The lateral borders are nearly level ; above and behind the external border 

 is remarked a considerable eminence, formed by the bone which will be 

 hereafter studied as the supercarpal bone (or trapezium). 



In the carpus of the Horse are seven bones, which are disposed in two 

 superposed rows. The superior row comprises four bones placed side by 

 side, and designated by the numerical names of first, second, third, and fourth, 

 viewing them from without to within. The inferior row has only three, 

 which are named in the same manner. 



