312 THE SKELETON. 



with the articular surfaces of the tibia and fibula, and also of the scaphoid and cuboid. The 

 remaining portion of the tarsus is then brought into contact with the sawn surfaces of the tibia 

 and fibula, and fixed there. The result is a position of the shortened foot resembling talipes 

 equinus. Watson's operation is adapted to those cases where the disease is confined to the 

 anterior tarsal bones. By two lateral incisions he saws through the bases of the metatarsal 

 bones in front and opens up the joints between the scaphoid and astragalus, and the cuboid and 

 os calcis, and removes the intervening bones. 



The metatarsal bones and phalanges are nearly always broken by direct violence, and in the 

 majority of cases the injury is the result of severe crushing accidents, necessitating amputation. 

 The metatarsal bones and especially the one of the great toe, are frequently diseased, either in 

 tubercular subjects or in perforating ulcer of the foot. 



Sesamoid Bones. 



These are small rounded masses, cartilaginous in early life, osseous in the adult, 

 which, are developed in those tendons which exert a great amount of pressure upon 

 the parts over which they glide. It is said that they are more commonly found in 

 the male than in the female, and in persons of an active muscular habit than in 

 those who are weak and debilitated. They are invested throughout their whole 

 surface by the fibrous tissue of the tendon in which they are found, excepting upon 

 that side which lies in contact with the part over which they play, where they 

 present a free articular facet. They may be divided into two kinds : those which 

 glide over the articular surfaces of joints, and those which play over the cartilag- 

 inous facets found on the surfaces of certain bones. 



The sesamoid bones of the joints in the upper extremity, are two on the palmar 

 surface of the metacarpo-phalangeal joint in the thumb, developed in the tendons 

 of the Flexor brevis pollicis ; occasionally one or two opposite the metacarpo- 

 phalangeal articulations of the fore and little fingers ; and, still more rarely, one 

 opposite the same joints of the third and fourth fingers. In the lower extremity, 

 the patella, which is developed in the tendon of the Quadriceps extensor ; two small 

 sesamoid bones, found in the tendons of the Flexor brevis hallucis, opposite the 

 metatarso-phalangeal joint of the great toe ; and occasionally one in the metatarso- 

 phalangeal joint of the second toe, the little toe, and, still more rarely, the third 

 and fourth toes. 



Those found in the tendons which glide over certain bones occupy the following 

 situations : one sometimes found in the tendon of the Biceps cubiti, opposite the 

 tuberosity of the radius : one in the tendon of the Peroneus longus, where it glides 

 through the groove in the cuboid bone ; one appears late in life in the tendon of the 

 Tibialis anticus, opposite the smooth facet of the internal cuneiform bone ; one is 

 found in the tendon of the Tibialis posticus, opposite the inner side of the head of the 

 astragalus ; one in the outer head of the Gastrocnemius, behind the outer condyle 

 of the femur; and one in the conjoined tendon of the Psoas and Iliacus, where it 

 glides over the os pubis. Sesamoid bones are found occasionally in the tendon of 

 the Gluteus maximus, as it passes over the great trochanter, and in the tendons 

 which wind round the inner and outer malleoli. 



