TISSUES OF THE BODY. 243 



neous, but by no means very transparent appearance : it is, on the con- 

 trary, tolerably dull and opaque. If we -employ very strong magnifying 

 powers, we remark at times, with tolerable clearness, a finely-dotted ap- 

 pearance in the mass. Owing to this, many histologists (Todd and Sow- 

 man, Toiiies and Koelliker) look upon the texture of the tissue as being 

 granular, which is denied by others (Henle and Gerlacti). It appears 

 more than probable, however, that the transverse sections of the finest 

 of the canaliculi, though they do not entirely produce this appearance, 

 do play some part in it. 



In transverse sections, likewise, we may distinguish on every Haversian 

 lamella, with more or less distinctness, an external and more deeply shaded, 

 and an internal and much lighter part a difference the significance of 

 which is doubtful. 



Attention has been directed rather recently to a peculiar system of fibres 

 in the ground-mass of osseous tissue, namely, to the perforating fibres of 

 Sharpey (fig. 235), (Sharpey, H. Muller, Koelliker (2), Gegenbaur). They 

 are to be found in human bone and that of other mammals, but more 

 frequently still in that of amphibia and fishes, appearing with a certain 

 irregularity and variableness. 



Those systems of lamellae which are formed by the periosteum, namely, 



the general lamina), as well as 

 the more superficial of the Ha- 

 versian system, are pierced by 

 the fibres in question, sinking 

 into them from the perios- 

 teum " like the leaves of a 

 book by a nail which has been 

 driven through them." They 

 are frequently enlarged at one 



Fig. 23-5. Sharpens fibres (6) of a penosteal lamella, from prif l i nto a fimnpl <*harp "hut 

 the human tibia, a c, osseous cell-cavities. nnel sna P e > Dut 



may also be pointed or branched , 



&c. In certain localities they enter into the construction of a network, some- 

 times wide and sometimes narrow, in its meshes. In the hollow bones of 

 amphibia and mammals (fig. 236) this system of fibres consists of longitu- 

 dinal columns (b b), from which radiating systems of branches (cc) pass off, 

 piercing the lamella in the direction of the periosteum, as well as towards 

 the Haver sian canals. 



In the substance of these fibres, but especially in their nodal points, we 

 may encounter osseous corpuscles. Sharpens fibres are connected with 

 the periosteum; they are the residue of connective-substance, i.e., of 

 bundles of connective-tissue dating from the period of the formation of 

 those lamellaB. The cells contained in their cavities have the significance 

 of connective-tissue corpuscles also (Gegenbaur}. The chemical bearing 

 also of these mostly calcified fibres agrees likewise with this view. In 

 keeping with their origin from the periosteum, they must be absent in the 

 systems of leaves, filling up the Haversian spaces (fig. 234). 



The most important elements of osseous tissue, however, are the cells 

 of the latter, imbedded in it in the greatest abundance, and situated in 

 the enlarged and radiating nodal points of a highly-developed system of 

 canaliculi traversing the hard osseous substance. 



With these, therefore, we must occupy ourselves before passing on to 

 anything else. 



This system of canals, whose finer branches are called canaliculi (Kalk- 



