70 THE ARTISTIC ANATOMY OF ANIMALS 



This disappearance of the lateral digits cannot excite 

 surprise when we consider the functions of the organs. 

 Becoming useless, they must undergo gradual atrophy from 

 want of use. 



There undoubtedly is, in this former existence of supple- 

 mentary digits in the horse, something analogous to what 

 we still find in the pig ; where the two principal digits are 

 accompanied by two shorter ones, which very probably, 

 from their infrequent use, are destined to disappear in a 

 more or less distant future. 



Proportions of the Arm, the Forearm, and the 



Metacarpus 



As a supplement to the study of the anterior limbs which 

 we have just finished, it appears necessary to give some 

 indications of the relative proportions of certain of the 

 segments which form these limbs in the plantigrades, the 

 digitigrades, and the ungulates. 



First, we would remark that, in following this order of 

 classification, the scapula becomes less and less narrow, 

 and assumes a form more and more elongated. In order to 

 convince ourselves of this, it will be sufficient to study the 

 bone first in man, then in the bear, the cat, dog, ox, and 

 finally in the horse. 



As to the proportions of length, which are those we 

 should chiefly study, we shall commence with the 

 comparison of the forearm and arm — that is to say, 

 the radius and the humerus. The radius is found to 

 be longer in proportion to the humerus, as the number 

 of digits is smaller, and the hand loses more and more the 

 functions of an organ of prehension. In man, the radius is 

 shorter than the humerus ; in the horse, on the contrary, it 

 is longer. 



To give an idea of this proportion, we shall employ what 

 is known as the antibrachial index. This index gives the 

 relation which exists between the length of the forearm and 

 that of the humerus ; the length of this latter, whatever 

 may be the actual measurement, is represented by a fixed 



