On the Trapezium of the Horse. 13 



From the above extracts it is seen that the trapezium 

 is held to be inconstant in its occurrence, about the size 

 of a pea when it is present, and of variable articulation. 

 Though these general facts are to be gathered from the text- 

 books, I am not aware that any more precise statements are 

 to be found in any publication. Seeing that the trapezium 

 is the bone of the carpus which has been most materially 

 affected by the process of reduction in number of the digits, 

 it appeared to the present writer that it would be well to 

 make some more detailed observations on its frequency of 

 occurrence, its size, and its articulation. To this end the 

 carpuses of twenty-nine horses were prepared in such a way 

 that there was no possibility of the trapezium being over- 

 looked if present. 



It was found difficult to estimate the size of the bones by 

 the eye ; and measurements by means of calipers did not seem 

 to afford any very precise information, because of the great 

 diversity in the stature of the animals from which the bones 

 were obtained. It was concluded that the best means of 

 denoting the size of the trapezium would be by computing 

 an index for each bone, taking the trapezoid from the 

 same carpus as being 100. The bones being irregular in 

 form, it was decided to abandon the use of calipers, and to 

 estimate the cubic capacity of each bone instead. This was 

 done by noting the amount of water displaced. In order to 

 guard against any error produced by absorption during the 

 process of estimation, each bone was soaked in water for 

 some time, then the adhering water was removed from the 

 surface with a cloth, after which the estimation was made. 



After the cubic capacity (size) of the trapezoid and trap- 

 ezium had been ascertained, an index was computed according 

 to the following formula : — 



Size of trapezium x 100 

 Size of trapezoid 



The following table, in which the size of the bones is given 

 in cubic centimetres, contains the results of the examination 

 of twenty-nine animals. Certain specimens, where only one 

 carpus could be obtained, are omitted. 



