138 THE CONNECTIVE TISSUES, BY A. EOLLETT. 



by Gegenbaur, Waldeyer, and Landois, in the works above 

 mentioned. The processes are more simple in animals where 

 successive lamellse only are deposited, but more complicated 

 when Haversian canals are developed, with their concentric 

 systems of lamellse. 



We shall in the first instance discuss the processes which 

 occur in the latter case, and for this purpose a transverse 

 section carried through one of the bones of the forearm of a 

 human embryo at the fifth month, invested with its periosteum, 

 may be advantageously studied (fig. 15). With low microscopic 

 powers we obtain from this the very instructive appearance 

 which is diagrammatically represented in fig. 15. The dia- 



Fijr. 15. 



Fig. 15. Transverse section through one of the bones of the forearm 

 of a human embryo, at the fifth month. (Half diagrammatic.) 



grammatic character of the illustration, however, relates only 

 to the tissue elements introduced into it. The dimensions of 

 the several layers being correctly indicated. 



A homogeneous smooth lamina may here be seen in the first 

 place constituting the outer layer of the periosteum, consisting, 



