ON TBE STRUCTURE AND DEVELOPMENT OF BONE. 14l 



possible to regard them as any other than osteogenic fibres. 

 This was the view taken by Sharpey, who was the first to 

 describe the tissue in question, and who was led to the conclu- 

 sion from the study of preparations torn or sliced from the 

 surface of the ossifying cartilage. In fact, in preparations so 

 made the appearance of the advancing ossification is almost pre- 

 cisely the same as that of the advance of ossification in the 

 parietal bone.' 



Nevertheless, Ranvier has seen fit to re-christen these sub- 

 periosteal osteogenic fibres of the " encoche d'ossification •" 

 with the name of " fibres arciformes.^' Moreover, he describes 

 them as being developed at the expense of the matrix of the 

 cartilage, and curving back from this to abut against the 

 surface of the newly formed periosteal bone, some even becom- 

 ing embedded in the osseous substance and transformed into the 

 perforating fibres of Sharpey. 



How M. Ranvier could have arrived at these conclusions I 

 am unable to conceive, unless he were misled by the examination of 

 sections which did not haj)pen to pass in or near the axis of the 

 b)ne. The figure (fig. 3, PL YII) represents with the utmost 

 fidelity the "encoche d'ossification " of the humerus of a cat- 

 embryo, and it in no way corresponds to Ranvier's description. 

 Moreover, I have seen similar appearances in scores of sections 

 from growing bones of a number of diftVrent species of animals. 



Sometimes bundles of connective-tissue fibres may be seen in 

 the encoche passing from the periosteum and crossing the direc- 

 tion of the osteogenic fibres (see fig. 2, PI. ^Wpf). It would 

 seem to be these that become the perforating fibres; the others, 

 I have no doubt, form here, as in the parietal, the reticulating 

 fibres of the perfect bone. 



The extension of the bony substance by osteogenic fibres 

 which pass in bunches from the ends of the osseous points or 

 spicules and intercross with those from adjacent points can also 

 be seen in the transverse section of a growing bone (Plate VII, 

 fig. 5). Here the fibres spread out in all directions in the 

 osteoblastic tissue ; they are totally distinct from the connective- 

 tissue [fibres of the -periosteum, which occur chiefly near the 

 outer surface of that membrane. 



I am indebted for the careful and elaborate drawings from 

 which most of tlie figures which serve to illustrate this note 

 have been executed to the facile pencil of Mr. John Lawrence, 

 one of the students in my class of histology. To the faithful- 

 ness of the drawings as copies of the preparations I can testify ; 

 as artistic productions they speak for themselves. 

 ' See Quain's 'Anatomy,' fifth edition. 



VOL. XVIII. NEW SER. K 



