16 Proceedings of the Royal Physical Society. 



It is noteworthy that the breed of horse has, so far as this 

 investigation shows, no effect upon the presence or absence 

 of the trapezium. 



The statement that the trapezium is about the size of a 

 pea, while sufficiently descriptive for ordinary purposes, is 

 not to be taken as absolutely accurate. The indices given 

 above range from 1*20 to 16; thus showing a very consider- 

 able variation in the relative size of the trapezoid and 

 trapezium. The 22 trapezia which are mentioned above 

 may be placed in four arbitrary groups, according to their 

 indices. Fourteen of the 22 are found to be contained in 

 the group of bones whose indices range from 5 to 9'99. 

 Four have an index below 5 ; three come between 10 and 

 14*99 ; and only one is so large as to have an index of 15 or 

 over. The outline drawing (Fig. 1) shows the relative size 

 of the trapezium and trapezoid in a carpus in which the 

 trapezium was slightly larger than the average. 



When the absolute size of the trapezium is taken into 

 account, it is found to vary from 0*1 c.c. to 1*4 c.c; the 

 variation not depending entirely upon the stature of the 

 animal, though it does so in the main. In this connection it 

 is perhaps worth noting that, where both limbs of the same 

 animal contain trapezia, the two bones are most frequently 

 of nearly equal size. The only exception given in Table I. 

 being carpus No. 1, in which the right trapezium (0*1 c.c.) is 

 much smaller than the left (0*8 c.c). 



In regard to the articulation of the trapezium, the 

 commonly accepted statement is sufficiently correct. Out 

 of the 25 bones, 6 were found to be entirely non-articular, 

 i.e., they were completely embedded in ligament. Of the 

 remaining 19 bones, only 6 articulated with the trapezoid 

 and the second metacarpal bone. About half (13) of the 

 trapezia found in the material used for this investigation 

 had only one articular surface, viz., for the trapezoid. The 

 articular area on the trapezoid for the trapezium varies in 

 extent, of course, in conformity with the degree of develop- 

 ment of the trapezium. In addition, it also differs in its 

 level. In some cases it is placed so high as to be continu- 

 ous with the articular surface for the scaphoid. In other 



