100 BONES OF THE LOWER LIMB. 



From -what is stated above it appears that in the bones of the arm and 

 forearm the epiphyses which meet at the elbow- joint begin to ossify later, and 

 unite with their shafts earlier, than those at the opposite ends of the bones, M'hile 

 in the bones of the thigh and leg the epiphyses at the knee-joint are the soonest 

 to ossify and the latest to unite with their shafts. In the bones of the arm and 

 foreaiTti the nutrient foramina are directed towards the elbow ; in those of the 

 thigh and leg they are directed away from the knee. Thus in each bone the 

 epiphysis of the extremity towards which the nutrient foramen is directed is the 

 first to be united to tlie shaft. 



The carpus is entirely cartilaginous at birth. Each carpal l)one is ossified from 

 a single nucleus. The nucleixs of the os magnum appears in the first year ; that 

 of the unciform in the first or second year ; that of the cuneiform in the third 

 year ; those of the trapezium and semilunar bones in the fifth year : that of the 

 scaphoid in the sixth or seventh year ; that of the trajjezoid in the seventh or 

 eighth year : and that of the pisiform in the twelfth year. 



The Metacarpal bones and Phalanges are usually fonned each from a prin- 

 cipal centre for the shafts and one epiphysis. The ossification of the shafts 

 begins about the eiglith or ninth week. In the four inner metacarpal bones the 

 epiphysis is at the distal extremity, while in the metacarpal bone of the thumb 

 and in the phalanges it is placed at the jjroximal extremity. In many instances, 

 however, as was kno^^ir to Albinus, and has been more fully showTi by Allen 

 Thomson (Jour, of Anat., LSfi'J), there is also a distal epiiAysis visible in the 

 first metacarpal bone at the age of seven or eight years, and there are even traces 

 of a proximal epiphysis in the second metacarpal. In the seal and some other 

 animals there are always two epiphyses in these bones. The epiphyses begin to 

 be ossified from the thiixl to the fifth year, and ai-e united to their respective 

 .shafts about the twentieth year. 



v.— THE PELVIS AND LOWER LIMB. 



The divisions of tlie lower limb are the haimch or hip, thigh, lej?, and 

 foot. In the haunch is the innominate l)oue, which enters into the 

 formation of the pelvis ; in the thigh is the femur ; in the leg the 

 tibia and fibula ; and at the knee a large sesamoid bone, the patella. 

 The foot is composed of three parts ; • the tarsus, metatarsus, and 

 phalanges. 



THE INNOMINATE BONE. 



The innominate bone, os coxa', or jwlvic hone, with its neighbour of 

 the opposite side and the addition of the sacrum and coccyx, forms the 

 pelvis ; it transmits the weight of the body to the lower limb. In 

 form it is constricted in the middle and expanded above and below, 

 and is so bent upon itself that the anterior margin of the upper part 

 looks outwards, while the lower part is directed inwards. On the 

 external aspect of the constricted portion is the acetahvhim, a cavity 

 which articulates with the femur, and perforating tlie inferior expan- 

 sion is a large opening, the olturator foramen. The superior wider part 

 of the bone forms part of the abdominal wall : the inferior enters into 

 the formation of the true pelvis. The innominate bone articulates 

 with its fellow of the opposite side, with the sacrum, and with the 

 femur. 



In the description of this bone it is convenient to recognise as 

 distinct the three parts of it which are separated in early life, viz., the 



