108 SESAMOID BONES. 



pairs of sesamoid bones included in the number of pieces which com- 

 pose the skeleton, two upon the metacarpo-phalangeal articulation of 

 each thumb, and existing in the tendons of insertion of the flexor 

 brevis pollicis, and two upon the corresponding joint in the foot, in 

 the tendons of the muscles inserted into the base of the first phalanx. 

 In addition to these there is often a sesamoid bone upon the meta- 

 carpo-phalangeal joint of the little finger ; and upon the corresponding 

 joint in the foot, in the tendons inserted into the base of the first 

 phalanx; there is one also in the tendon of the peroneus longus 

 muscle, where it glides through the groove in the cuboid bone ; some- 

 times in the tendons, as they wind around the inner and outer 

 malleolus ; in the psoas and iliacus, where they glide over the body of 

 the os pubis ; and in the external head of the gastrocnemius. 



The bones of the tympanum, as they belong to the apparatus of hear- 

 ing, will be described with the anatomy of the ear. 



