234 SKELETON. 



joining the second. The anterior extremity is rough, for the at* 

 tachment of the adjoining soft structure. This phalanx of the 

 fourth and fifth toe is frequently very imperfectly developed, be- 

 ing a mere tubercle with an articular face at one end. 



The structure of the metatarsal and phalangial bones resem- 

 bles that of other long bones. Porous and cellular at the ex- 

 tremities, their bodies are composed of compact lamellated mat- 

 ter, enclosing a cancellated texture. 



SECT. IV. OF THE DEVELOPMENT OF THE INFERIOR EXTREMITIES. 



The comparatively small quantity of blood which is sent to the 

 lower extremities of the foetus, is the cause of their not being so 

 large in proportion to the upper, at the time of birth, as they are 

 subsequently. Our wants immediately after birth, and during 

 the first months of life, are naturally such as to require but little 

 service from the lower extremities, in which is seen a striking 

 correspondence between the internal arrangements of the animal 

 economy and its actual necessities; or, in other words, a conti- 

 nued and rigid adaptation of means to produce a certain effect. 



The os femoris at birth presents several peculiarities. The su- 

 perior extremity being in a cartilaginous state, is placed more at 

 :. right angle to the body of the bone than it is in the adult. The 

 neck is short, which by diminishing the base of support to the' 

 trunk, makes the progression of infants more tottering and infirm. 

 The lower extremity is also cartilaginous and large. The body 

 of the bone has but a very slight degree of curvature, which like- 

 wise increases the difficulty of standing and walking in very 

 young subjects. The patella is cartilaginous. 



In the leg the bodies of the tibia and fibula are ossified, but 

 their extremities are cartilaginous. The bones of the tarsus, 

 with the exception of parts of the os calcis and of the astragalus 

 are cartilaginous. The metatarsus and the phalanges are ossi- 

 fied in their middle, but cartilaginous at their extremities: their 

 development is not so complete as that of the corresponding 

 bones of the hand. 



