OSSIFICATIOX OF SHOULDER BONES. 



95 



more compressed antero-posteriorly, are divided by a shallow groove into 

 two condyles. 



Those of the muldlo row are four in number. Smaller than those of the 

 preceding set, they resemble them in form, with this difference, that 

 their proximal extremities present, on the articular surface a slio-ht 

 middle elevation and two lateral depressions, adapted to articulate with 

 the condyles of the first phalauges. 



The terminal or ungual phalanges, five in number, have proximal 

 extremities similar to those of the middle row, but with a rough 

 depression in fi'ont, where the flexor tendons are inserted. They taper 

 towards their somewhat flattened and expanded free extremities, which 

 are rough and raised round the margins and upon the palmar aspect in 

 the ungual process. 



Sesamoid boxes. — A pair of sesamoid bones is placed in the palmar 

 wall of the metacarpo-phalangeal articulation of the thumb ; and 

 similar nodules, single or double, are sometimes found in the corre- 

 sponding joint of one or more of the other fingers, most frequently of 

 the index and little fingers. 



OSSIFICATION OF THE BONES OP THE UPPER LIMB 



With the exception of the clavicle, all the bones of the upper limb begin to 

 ossify from cartilage. 



The scapula is ossified fi-om a single osseous nucleus for the body, and addi- 

 tional centres for the coracoid process, acromion, base, and lower angle. The 



Fig. 81. 



0^ 



1 year. 15 or 16 years. 17 or IS years. 22 years. 



Fig. SI. — Ossification of the Scapula (K. Quain). 



A, about one yeai-. 1, shows the large spreading ossification, from the primary centre. 

 2, the commencing nucleus in the coracoid process. 



B, about fifteen or sixteen years. The coracoid process (represented as too little 

 ossified in the figure) is now partially united at its base ; a nucleus, 3, has appeared 

 in the acromion, and another, 4, at the lower angle. 



C, male scapula at seventeen or eighteen years ; a second point, 5, has appeared in the 

 acromion, and ossification has advanced into the ridge of the base, 6. 



D, the scapula of a man of about twenty-two years of age ; the acromion and the ridge 

 of the base are still separate. B, C, and D, are about the fourth of the natural size. 



