ON THE STRUCTURE AND DEVELOPMENT OF BONE. 135 



in consequence of the soft nature of the interlamellar ground- 

 substance as compared with the fibrillated bundles of which the 

 lamellae are mainly composed. 



We are led therefore from these comparisons to the conclusion 

 that each lamella of bone consists of a layer of fibres crossing 

 obliquely in two directions, covered on both surfaces by and 

 embedded in a homogeneous ground-substance, which is con- 

 tinuous between the fibres, and also fused wnth the ground sub- 

 stance of adjoining lamellse; the planes of separation between 

 the lamellae being in the fully-formed bone indicated by the 

 presence of the flattened lacunae. 



II. Natwre of the Perforating Fibres of Sharpen/. — It is now 

 generally admitted that the perforating fibres agree in their 

 general appearance and intimate structure with the bundles of 

 tendon or ligament, with the exception, of course, that they have 

 undergone calcification. This view is further strengthened by 

 the fact that many of them are to be traced directly from the 

 fibrous tissue of the periosteum : ' moreover, as Ranvier has 

 pointed out, wherever a tendon or ligament is inserted into 

 bone, the bundles of fibres of the tendon or ligament are con- 

 tinued into the bone as perforating fibres. On the other hand 

 it is to be remarked that the latter differ from tendon-bun- 

 dles in the fact that they are not overlaid by flattened cells. In 

 micro-chemical reactions also the ordinary perforating fibres of 

 Sharpey agree with tendon-bundles, swelling up with acids 

 and so on. Heinrich Miilier, however, remarked that some of 

 the perforating fibres were of the nature of elastic tissue, basing 

 this opinion chiefly upon the resistance they offered to the action 

 of acids. My present purpose is to show how these elastic per- 

 forating fibres can readily be distinguished in situ, and differen- 

 tiated from those of the white variety. 



The process consists in staining sections of the softened bone 

 with magenta. This dye has a singular affinity for elastic tissue, 

 and it suffices to mount the sections, after every trace of the 

 acid which has been used to decalcify the bone has been washed 

 away, in a solution of magenta in glycerine and water. The fluid 

 should be only sHghtly coloured, and the edges of the coverglass 

 must be at once cemented so as to prevent evaporation of the 

 water. This is necessary, because concentrated glycerine re- 

 dissolves any of the colouring matter that has been deposited in 

 the tissue, and for a similar reason it is not possible to use an 

 alcoholic solution. 



' Tbis by no means applies universally, for groups are often to be found 

 •which commence near the medullary canal, generally close to the circum- 

 ference of a Haversian system, and the fibres of which taper off before 

 reaching the periosteum. Fide Plate VII., fig. 1, pf. 



