On the Trapezium of the Horse. 11 



Arloing (1) also, at one time, was of opinion that the chief 

 metacarpal bone of the horse consists, in reality, of the 3rd 

 and 4th metacarpal bones ; an opinion shared by Chauveau.^ 



It is evident from the above that the earlier thinkers 

 inclined to the supposition that the reduction in the number 

 of metacarpal bones of the horse has been produced by the 

 union of previously independent structures; a supposition 

 engendered by the then domination of comparative anatomy 

 by human anatomy. The application of the " fusion " hypo- 

 thesis was not confined to the metacarpus, but was extended 

 to the carpus : Daubenton, for instance, stating that if there 

 are not eight bones in the horse's carpus, it is because the 

 trapezoid is blended with the magnum. 



The testimony of the rocks has convinced morphologists 

 that the reduction in the number of both carpal and meta- 

 carpal bones is due to the gradual reduction in size, and 

 final disappearance of elements present in the predecessors 

 of the horse. Since it is only proposed to devote attention 

 to the frequency of occurrence of a carpal bone, which there 

 is no reason to doubt is at present in process of disappearance, 

 it is quite beyond the province of the present short com- 

 munication to consider the evidence of fossil remains. It 

 will suffice to say that there is abundant proof that the 

 trapezium bone (ps multangidum majus, os carpale primum) 

 was present in the carpus of the extinct animals from which 

 the modern horse has descended. Further, it is a constant 

 component of the carpus of present-day allied genera of the 

 horse. 



In the horse, as we now know it, the trapezium is not 

 infrequently entirely absent. That this has been recognised 

 for a considerable time is shown by an examination of the 

 older text-books dealing with the anatomy of the horse. 

 For example, Percivall (2), writing in 1858, states (p. 52) 

 that " it (the carpus) is composed of seven small bones : in 

 some instances an eighth has been found." 



Modern writers are naturally more precise in their state- 

 ments, as may be gathered from the following quotations 



1 Both Arloing and Chauveau have changed their opinions, in accordance 

 with facts unknown at the time of the appearance of their earlier publications. 



