OF THE MOTOEY APPARATUS IN MAN. 145 



and an articulated lever, formed of three principal parts 

 the thigh, the leg, and the foot corresponding to the arm, 

 the fore-arm, and the hand. 



279. The haunch or basilar portion of the abdominal or 

 pelvic extremity is composed of one bone on either side, the 

 os innominatum or haunch-bone. In the young this bone 

 is composed of three large portions, called pubic, iliac, and 

 ischiatic portions. These have been considered analogous to 

 the scapula, coracoid process, and clavicle. These bones, the 

 ossa innorninata, are articulated in the most solid manner with 

 the sacrum by strong articulations, and with each other at 

 the pubis ; these joints are immovable in their normal state : 

 with the sacrum and coccyx, the innominata form the osseous 

 girdle, called the pelvis, surrounding the lower part of the 

 trunk. To this basin or pelvis are consequently attached the 

 powerful erectors of the spine, the muscles which are to 

 move the lower extremities, and those which shut in the 

 abdominal and pelvic cavities. 



280. In the thigh there is but one bone, the femur 

 (Pig. 94). The head of this bone, by which it articulates 

 with the pelvis, forms, with the cotyloid cavity of the haunch - 

 bone, a perfect ball-and-socket joint, protected by a capsular 

 ligament, permitting of circular movements, or nearly so. 

 A short neck (cervix) connects the spherical head of the 

 femur to a powerful cylindrical shaft, which enlarges towards 

 its lower extremity, by which it articulates with the tibia. 

 This is by much the longest and strongest bone of the body. 

 Powerful muscles surround and move it in all directions, 

 excepting backwards or in extension. 



281. The skeleton of the leg is composed of two 

 bones, the tibia and fibula. The rotula or patella, attached 

 to the tibia by a powerful ligament, or rather tendon, is a 

 sesamoid bone, developed in a fibro- cartilage connected with 

 the system of the tendons. The tibia carries the whole 

 weight of the body, transmitted to it through the femur, 

 which it transmits to the astragalus. There is no rotation at 

 the knee-joint in general, nor at the ankle. The malleoli 

 formed by the lower ends of the tibia and fibula assist in 

 forming a case for the head of the astragalus. 



282. The foot, like the hand, is divided into three 



regions : the tarsus, metatarsus, and toes. In the tarsus 



there are seven bones, the astragalus, os calcis, scaphoid, 



cuboid, and three cuneiform bones ; in the metatarsus there 



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