132 E. A. SCHaFER. 



Notes on the ^Structure and Development of Osseous 

 Tissue. Bj E. A. Schafer. With Plates VII and VIII. 



{From the Physiological Laboratori/ of University College, London.) 



I. The lamellae of bone. — That the lamellae when stripped off 

 from a bone that has been softened in acid but subsequently 

 completely freed from all traces of the acid by long steeping in 

 water or spirit exhibit under the microscope an appearance of 

 intercrossing fibres (the reticulating fibres of Sliarpey), is a 

 familiar fact to every student of histology in this country. But 

 in spite of its obvious importance and of the ease with which 

 the fact can be demonstrated, it has been, if not actually denied, 

 at least ignored by Continental writers almost w^ithout excep- 

 tion. 



It is not, however, only in preparations of decalcified bone 

 that these fibres may be observed, nor does the fact of their 

 existence depend upon the appearances seen in a lamella when 

 viewed on its surface; for the assumption of the existence of 

 fibres in the lamella afl'ords the only rational explanation of 

 what is seen in a section of the bony layers made perpendicular 

 to their surface. In such a section, taken we will suppose for 

 sirapHcity of description across a Haversian system, we find 

 concentric rows of angular dots which are embedded in a homo- 

 geneous substance, an appearance of alternating granular and 

 clear zones being thus produced. Sections of the flattened cell- 

 cavities (lacunae) occur here and there in the clear zones, but 

 except where the lacunae are present the homogeneous osseous 

 substance is continuous throughout the Haversian system, being 

 only partly interrupted by the concentric rows of angular dots. 

 The question therefore arises. What in the section shall be taken 

 to represent a single lamella ? 



Before endeavouring to supply the answer, it will be well to 

 consider the opinions of previous authors who have given special 

 attention to the subject. Sharpey described the appearances as 

 follows '} — " In a thin transverse section of hard bone the con- 

 centric lines, or rather bands, which represent the cut edges of 

 the lamellae, generally present with transmitted light a dark 

 granular-looking, and a light, transparent, and usually narrower 

 zone. ... In a decalcified section the dark part shows a multi- 

 tude of short bright lines running radially across it, with dark 

 angular particles between them . . . the appearance of dark 

 particles seems to be produced by the cut ends of the reticulat- 

 • Quiiiii's 'Anatomy,' seventh edition. 



