42 HORSE AND MAN. 



of the true shape of either the coffin or navicular 

 bones, two views of each are here presented. 



What might be the origin of this bone was for 

 some time a matter of controversy. It was long 

 thought to be a modification of one of the missing 

 bones of the foot, but is now known to be a 

 ' sesamoid ' bone. There are many of these bones, 

 variously formed in different animals, the largest 

 being the knee-cap, or ' patella.' They are developed 

 within the tendons, and derive their rather fanciful 

 name from their usually small size, together with 

 their shape, which bears some resemblance to that of 

 the sesame seed. 



The reader will see that the navicular lies behind 

 the coffin bone, and between the two wings. Its 

 chief object is to act as a pulley, so as to enable the 

 foot to be bent, or ' flexed,' with greater force. 



Another sesamoid bone, performing a similar 

 office, may be seen at f, just at the end of the cannon 

 bone, and aids in producing the characteristic pro- 

 jection at the beginning of the pastern. At T is seen 

 the fatty cushion of the pastern. Its structure acts 

 as a guard to the delicate machinery of the sesamoid 

 bone and tendon. 



We are now led to another element in the horse's 

 foot — namely, the tendons — i.e. the ligamentary 

 bands by which the muscles act on their attachments. 



