ON THK STRUCTURE AND DEVELOPMENT OF BONE. 137 



Fibres. — I am not aware that it has hitherto been attempted to 

 identify the intercrossing fibres which are seen in the developed 

 osseous tissue witli any of the appearances exhibited by bone 

 which is in progress of development. And this is scarcely to 

 be wondered at, considering that most writers have ignored the 

 very existence of those fibres. It seems nevertheless surprising 

 that no one should have, at least so far as my knowledge 

 of the matter extends, offered any conjecture respecting 

 the destination of the osteogenic fibres, which are so charac- 

 teristic of the true intra-connective ossific process. It is 

 generally assumed that by the extension of the calcific deposit 

 into them and by a deposit of a material similar to that of 

 which they are composed, upon and between them, they 

 become altogether blended, and that as distinct fibres they 

 are entirely obliterated. On the contrary, I would venture to 

 conclude that so far from this being the case the osteogenic fibres 

 persist as the intercrossing fibres of Sharpey} 



In order to make clear the reasons upon which this opinion 

 is based, it is desirable that the mode of advance of the ossific 

 process into a connective-tissue membrane should be exactly 

 understood. We will therefore first of all consider the details 

 of the process as it proceeds in the membrane-skull and in the 

 perichondrium of the long bones respectively. 



a. Ossification of one of the Membrane Bones of the Skull. — 

 The advancing edge of the growing bone is jagged in outline (Plate 

 VIII, fig. 1), the bony matter shooting out into the contiguous 

 membrane in the form of pointed processes, the so-called 

 " spicules," to which the deposit of earthy salts in the form of 

 minute globules gives a coarse granular appearance. Each 

 spicule is prolonged into the adjoining connective tissue by a 

 bunch of long, straight, unbranched delicate fibres, the osteo- 

 genic fibres. These themselves show an indication of fibrilla- 

 tion, and on this account and because of the similarity in 

 chemical constitution, they are regarded by Gegenbaur as 

 simply connective-tissue bundles of the fibrous membrane. It 

 is possible that they may pass into true connective-tissue 

 bundles at their further extremity, but this is by no means 

 certain, nor do I think that it has been ever clearly made out. 

 At any rate here, close to the advancing calcification, they are 

 quite diti'erent in general appearance from the connective-tissue 



^ Not as the perforating fibres, as Clemeuti (in a paper which he has 

 published lately, and which he makes au ill-supported claim of priority of the 

 discovery of tlie perforating fibres on behalf of tiie Italian anatomists) 

 wrongly makes Gegenbaur assert, dementi's paper is more fully dealt 

 with in the letter which follows this article. See also fartlier on for a 

 criticism of Kanvier's views as to the origin of the perforating fibres. 



