OSTEOLOGY. 59 



The second phalangeal articulation is the same, and the 

 ungual phalanx presents a rough, arrow-shaped extremity. 



The muscular insertions to the first row are : to thumb four, 

 flexor brevis, abductor and adductor pollicis, and extensor primi 

 internodii ; to index two, first palmar and dorsal interosseus ; to 

 middle two, second and third dorsal interossei; to ring two, 

 second palmar and fourth dorsal interosseus; to little three, 

 flexor brevis and abductor minimi digiti and third palmar inter- 

 osseus. 



The insertions to second row are: extensor secundi inter- 

 nodii and flexor longis pollicis; and to each of the others four, 

 extensor communis digitorum, flexor sublimis digitorum, with 

 the addition of extensor indicis to index and extensor minimi 

 digiti to little. 



The insertions to third row are: extensor communis digi- 

 torum and flexor profundus. 



Ossific centres are two for each bone, one each for shaft 

 and base. 



THE LOWER EXTREMITY. 



The lower extremity consists of the thigh, leg, and foot. It 

 is connected to the trunk by the haunch, or hip-bone, and contains 

 the following bones: os innominatum, femur, patella, tibia, 

 fibula, seven tarsus, five metatarsus, and fourteen phalanges. 



THE os INNOMINATUM, or hip-bone, is a large, irregular bone 

 forming the lateral and anterior walls of the pelvis, and consist- 

 ing of three bones, ilium, ischium, and pubes, united about 

 puberty. It presents 



The acetabulum or cotyloid cavity, a deep, cup-shaped cavity, 

 for articulation of the head of the femur the ischium forming 

 a little more than two-fifths, the ilium a little less than two- 

 fifths, and the pubes one-fifth. The bottom of the cavity presents 

 a circular depression, lodging a mass of fat, and giving attach- 

 ment by its edges to the ligamentum teres, and continuous below 

 with a deep notch, the cotyloid notch, for attachment of cotyloid 

 and part of ligamentum teres, converted into a foramen by the 

 transverse ligament for the entrance of the nutrient vessels and 

 nerves. The margin of the acetabulum is deepened by a fibro- 

 cartilaginous ring. 



The obturator, or thyroid foramen, is an aperture large and 

 ovoidal in the male, small and triangular in the female, situated 

 on the anterior inferior surface between tho ischium and pubes. 

 It is closed, in the recent state, by a strong membrane attached 

 to its margins except above externally, where a foramen exists 

 for obturator vessels and nerve. 



