16 



OSTEOLOGY. 



of being equally distributed throughout the matrix, become 

 arranged in parallel groups, and increase in number those nearest 

 the point of ossification enlarging. Matter, in the form of very 

 minute granules, is now deposited in this column of intercellular 

 or hyaline substance, as well as between each cell. 



Ossification of the cell walls ensues, which is followed by the 

 absorption of the osseous matter between the cells, converting 

 what was a row of closed cells into a tube, which is a rudiment- 

 ary Haversian canal, no trace being left of the nucleus of the 

 original cartilage corpuscle ; but there are numerous very minute 

 reddish granules, which almost fills the cavity, and are concerned 

 in the formation of blood-vessels, which now begin to appear. 

 The ossific parietes of the cartilage cells lining the tube, at first 

 thin, enlarge and thicken by successive layers of dense osseous 

 matter, and thus produce the concentric lamellae, the lamella last 



^fc0 



M: 



: nf o.ifyiiig cartilage magnified. On the left the cells are 

 ,1,' ;uT.-in<_'rd iii rows ; while to the right, between the rows, the 

 earthy material is being deposited. 



formed pushing out the older one, until what was the lining of 

 the tube becomes the external lamella of an Haversian system; 

 while the ossific matter which was deposited in the column of 

 intercellular material, becomes the connecting lamella between 

 the Haversian cylinders. 



In long bones this ossific process commences in the centre of 

 the shaft, gradually spreading to the extremities, in which there 

 are separate points of ossification; there are generally three such 

 points, one for the shaft, and one for each extremity, the develop- 

 ing shaft being called the c//fy;A //*<*', the extremities the epiphyses. 

 When any process is superadded, as the trochanter of the femur, 

 which possesses a distinct point of ossification, it may be termed 

 an cipophysis. As ossification commences in the shaft, there are 

 for some time after birth, intervening portions of unossified 

 cartilage, marked by a deep ring in the dried long bones of 



