142 THE CONNECTIVE TISSUES, BY A. ROLLETT. 



to those which are obtained from the early stages of develop- 

 ment of the so-called investing bones. 



The ossification of the investing bones, the so-called intra- 

 membranous ossification, was first distinguished from the in- 

 tra-cartilaginous by Nesbitt,* and subsequently by Sharpey .-f 

 The description of intra-membranous ossification given by 

 Sharpey was substantiated by Kolliker, and in consequence 

 obtained general acceptance. The finer details of this mode 

 of ossification may be found in the recent observations pub- 

 lished by LieberkiihnJ and Waldeyer. 



The expanded portion of the occipital bone, the parietal and 

 frontal bones, the squamous portion of the temporal bones, the 

 ossa Wormiana, and the facial bones are all developed in mem- 

 brane. The clavicle was included in the number of these bones 

 by Nesbitt and Bruch, but incorrectly, as was shown by H. 

 Miiller|| and Gegenbaur.lF The development of those bones 

 which are not formed in cartilage proceeds, however, like them, 

 from one or from a limited number of points. The tissue in which 

 these bones originate exhibits a great similarity to that which 

 has been already described as the second layer of the periosteum, 

 or as constituting the young medulla within the rings of well- 

 defined osteoblasts. In this tissue there first appear at the 

 points from which the ossification commences, small thin 

 trabeculse, which unite in a plexiform manner, and this differ- 

 entiation of tissue progressively extends in a radiating direc- 

 tion. The spaces enclosed by the anastomosing trabeculse are 

 wider towards the periphery than at the point from whence the 

 ossification commenced. Towards the periphery the trabeculse 

 are also thinner, and form finely pointed and radially directed 

 processes, and after assuming this arrangement become calcified 

 and converted into bone. If we examine such trabeculse before 

 they have undergone ossification, it will be seen that they 



* Osteogeny, etc., translated by J. C. Greding. Altenburg, 1753. 



t Quain's Anatomy, by Quain and Sharpey, fifth edition. 



| Reichert and Du Bois' Archiv, 1864, p. 610. 



Loc. cit., p. 368. 



|| Loc. cit., p. 201. 



If Jenaische Zeitschrift, 1864, p. 1. 





