THE HORSE : A ZOOLOGICAL STUDY. 203 



cannot enter into detail here, but I must ask you to accept my state- 

 ment that facts and observations are becoming multiplied to such an 

 extent as to cause the hitherto accepted view to totter and to need 

 its defenders to rally round it. Suffice it for us now to look upon 

 the foot of the horse as a great scientific bone of contention in the 

 future and a most beautiful piece of mechanism which ensures 

 our horses treading firmly and progressing rapidly in the present. 

 There are some horny portions of the limbs which are less interest- 

 ing practically than the hoofs, but equally instructive and curious to 

 the enquiring mind. The little knot of horn in the fetlock termed 

 the Ergot is considered to be a remnant of the hoofs of the two digits 

 represented by the splint bones. This little organ is rudimentary, 

 i. e.. of no known use in the present day, and it is only found in the 

 coarser breeds of horses. Another relic of the past, an organ in 

 process of disappearance, is that piece of horn inside the forearm, 

 where it is termed the Chestnut, and that inside the hock, where it is 

 termed the Castor; it corresponds to the finger nail of the thumb 

 of our hand and of the foot of the five-toed ancestor of the horse 

 in the very remote past. 



A lecturer on the processes of change going on in the body of 

 mammals, whereby variation is brought about, could find no struc- 

 ture better illustrative of the phenomena to be described than the 

 limbs of the horse. "Convergence," that is, similarity produced 

 by similar uses, would be illustrated by comparing the fore limbs 

 with the hind; " divergence" by showing how these two parts differ. 

 The sesamoid bones of the fetlock and the navicular bone show how 

 new bones appear and gradually increase in importance ; and the 

 splint bones, fibula and ulna, indicate the several ways in which 

 bones disappear, i. e., by degeneration, anchylosis, fusion, and develop- 

 mental absorption. The shoulder girdle of the horse is a specially 

 interesting study in comparative anatomy ; of the typical three ele- 

 ments, scapula, coracoid, and clavicle, the former is remarkably 

 well developed, the coracoid has degenerated into a single process of 

 the scapula, and the clavicle has become but a fibrous band in 

 the substance of the muscles running from the neck to the shoulder. 

 It is a fact not known to zoologists in general that the horse has 

 distinct indications of a clavicle, and that it is not rare to find in 

 him rudimentary clavicular muscles. The spine of the horse is in a 

 singular state of unrest. There is not one of its five regions that 

 has always the same number of bones. This is a most remarkable 



