six centres; one for the 

 first piece or manubrium, 

 four for the second piece 

 or gladiolus, and one for 

 the ensiform appendix. 

 The sternum is entirely 

 cartilaginous up to the mid- 

 dle of foetal life, and when 

 ossification takes place, the 

 ossific granules are depo- 

 sited in the middle of the 

 intervals between the ar- 

 ticular depressions for the 

 costal cartilages, in the fol- 

 lowing order (fig. 71): in 

 the first piece, between the 

 fifth and sixth months; 

 in the second and third, 

 between the sixth and se- 

 venth months ; in the fourth 

 piece, at the ninth month ; 

 in the fifth, within the first 

 year, or between the first 

 and second years after 

 birth ; and in the ensiform 

 appendix, between the se- 

 cond and the seventeenth 

 or eighteenth years, by a 

 single centre which makes 

 its appearance at the upper 

 part, and proceeds gra- 

 dually downwards. To 

 these may be added the 

 occasional existence, as 

 described by Breschet, of 

 two small episternal cen- 

 tres, which make their ap- 

 pearance one on each side 

 of the interclavicular notch. 

 These are regarded by him 

 as the anterior rudiments 

 of a rib, of which the pos- 

 terior rudiment is the ante- 

 rior lamina of the trans- 

 verse process of the seventh 

 cervical vertebra. It occa- 

 sionally happens that some 

 of the segments are form- 

 ed from more than one 

 centre, the number and posi- 

 tion of which vary (fig. 73). 

 Thus the first piece may 

 have two, three, or even 

 six centres. AV 1 icn two are 

 present, they are generally 

 situated one . above the 

 other, the upper one being 



STERNUM. 115 



Fig. 71. Development of Sternum, by Six Centres. 



Cartilage 



rarely unite > 

 except tiio&Za.yc 



3S-lfO. 

 I 20-25$ year 



| soon after puberty 



jja/rUy cartilaginous in, 

 ativaaaed life 



Figs. 73 and 74. Peculiarities. 



for 1??j)t*ee Zor ware rent? 

 jtt? putt, usually one 



And in 



ftfode of 

 Union 



of D ev el op -me r 



of lateral jjuctx producing 



Ster nsil fissure & 



-Sternal ford, me n 



