138 



THE BONES OF THE LOWER LIMB. 



7th week, and from four epiphyses, the centres for which appear in the following- order : A 

 single nucleus for the lower extremity appears shortly before birth, one for the head appears 

 in the 1st year, one for the great trochanter in the 4th year, and one for the small trochanter 

 in the 13th or 14th year. These epiphyses become united to the shaft in an order the reverse 

 of that of their appearance. The small trochanter is united about the 17th year, the great 

 trochanter about the 18th year, the head from the 18th to the 19th year, and the lower ex- 

 tremity soon after the 20th year. The neck of the femur is formed by extension of ossification 

 from the shaft. 



The patella is formed in the 3rd month by a deposit of cartilage in the tendon of the 

 quadriceps extensor cruris muscle. In this cartilage ossification begins from a single centre 

 during the 3rd year, and is completed about the age of puberty. 



Fig. 161. OSSIFICATION OP THE FIBULA. (R. Quain.) 



A, at birth ; the shaft is ossified, the ends are cartilaginous. 



B, at two years, showing a nucleus in the lower epiphysis. 



C, at about four years, showing the nucleus of the upper epiphysis ; the lower ought to have been 

 shown as more advanced. 



' D, at about twenty years ; the lower end is complete, but the upper epiphysis is still separate. 

 1, shaft ; .2, lower epiphysis ; 3, upper epiphysis. 



The tibia and fibula each present, besides the principal centre for the shaft, a superior 

 and an inferior epiphysis. In the tibia the centre for the shaft appears in the 7th week ; that 

 for the upper extremity, including both tuberosities and the tubercle, appears most frequently 

 before, but sometimes after birth ; and that for the inferior extremity and internal malleolus 

 appears in the 2nd year. The tubercle is occasionally formed from a separate centre.^ The 

 lower epiphysis and shaft unite in the 18th or 19th year, the upper epiphysis and shaft in the 

 21st or 22nd year. In the fibula the centre for the shaft appears rather later than in the tibia; 

 that for the lower extremity appears in the 2nd year, and that for the upper, unlike that of the 

 tibia, not till the 3rd or 4th year. The lower epiphysis and shaft unite about the 21st year, 

 the upper epiphysis and shaft about the 24th year. 



The fibula in the embryo at an early period is nearly as large as the tibia, and also articu- 

 lates with the femur. The tibial malleolus on the other hand is up to the seventh month of 

 foetal life longer than the fibular ; and the marked preponderance of the fibular malleolus, 

 which is peculiar to man, is only acquired after birth (G-egenbaur). 



The tarsal bones are ossified in cartilage each from a single nucleus, with the exception of 

 the os calcis, which in addition to its proper osseous centre, has an epiphysis upon its posterior 

 extremity. The principal nucleus of the os calcis appears in the 6th month of foetal life ; its 

 epiphysis begins to be ossified in the 10th year, and is united to the tuberosity in the 15th or 

 16th year. The nucleus of the astragalus appears in the 7th month ; that of the cuboid about 

 the time of birth ; that of the external cuneiform in the 1st year ; that of the internal cunei- 

 form in the 3rd year ; that of the middle cuneiform in the 4th year ; and that of the navicular 

 in the 4th or 5th year. 



The xnetatarsal bones and phalanges agree respectively with the corresponding bones of 

 the hand in the mode of their ossification. Each bone is formed from a principal piece and 

 one epiphysis ; and while in the four outer metatarsal bones the epiphysis is at the distal ex- 



