374 GENERAL ANATOMY. 



tance from it, and at a still greater distance homogeneous and 

 without vessels, but only perforated with some canals of blood- 

 vessels which tend towards the osseous centre. The osseous 

 point continually increases by growth at its surface, and also 

 by interstitial addition in its substance. The cartilage, suc- 

 cessively perforated by cavities and canals lined by sheaths of 

 blood-vessels, gradually diminishes in proportion as the bone 

 increases, and at length disappears. The canals of the carti- 

 lages themselves, which are very wide at the commencement 

 of ossification, become smaller and smaller, and at length dis- 

 appear when it is completed. In the place of a cartilage more 

 or less thick, but at first full or solid, without cavities and 

 without distinct vessels, at a later period perforated with ca- 

 nals lined by vascular and secreting membranes, there is found 

 a very vascular bone, full of areolar or spongy cavities, in- 

 vested with membranes and filled with adipose marrow. The 

 bone afterwards becomes less vascular as age advances. 



592. The cause of ossification, like that of organic forma- 

 tion in general, is unknown. From Hippocrates and Aristotle 

 to Scarpa, Bichat, and Mascagni, a multitude of more or less 

 ingenious hypotheses have been proposed on this obscure 

 subject.* 



It has been said, that the last divisions of the arteries ossify, 

 or are filled up with bony matter, and that after being filled 

 with bony matter, they burst, and allow it to escape around 

 them. It has also been said, and with more probability, that 

 they form, and allow to escape the ossifying matter, whether 

 by exhalent extremities, or by lateral porosities. But what 

 is this bony matter? Is it earthy substance? Where do the ar- 

 teries pour forth this substance? Is it in the interstitial areo- 

 laeof a cartilage, as has commonly been said since the time of 

 Herissant? or in absorbent vessels which are filled up, as Mas- 

 cagni alleged? These are so many mere hypotheses. All 

 that is known is this; that the vascularity greatly increases 

 before ossification, and that it always precedes that process; 

 that the cartilage diminishes and disappears in proportion as 



* See Scemmering, De, Corporis. Hum.fabricfi, T. 1. DC Ossibus. 



