xcvi BONE. 



of fibres, which pass through them in a perpendicular, or more or less 

 oblique direction, and, as it were, bolt them together. These perforating 

 fibres may be seen, with the aid of the microscope, in a thin transverse slice 

 of a decalcified cylindrical or cranial bone, on pulling asunder the sections 

 of the lamellae (as in fig. XLVL). In this way some lamellae will generally 

 be observed with fibrous processes attached to them (fig. XLVI. 6) of various 

 lengths, and usually tapering and pointed at their free extremities, but 

 sometimes truncated probably from having come in the way of the knife. 

 These fibres have obviously been drawn out from the adjacent lamellae, 

 through several of which they must have penetrated. Sometimes, indeed, 

 indications of perforations may be recognised in the part of the section 

 of bone from which the fibres have been pulled out (fig. XLVI. c). The pro- 

 cesses in question are thus, so to speak, viewed in profile ; but they may 

 frequently also be seen on the flat surface of detached lamellae, projecting 

 like nails driven perpendicularly or slantingly through a board (fig. XLVII. a) ; 

 whilst the lamellae at other parts present obvious apertures of considerable 

 size, through which the perforating fibres had passed (fig. XLVII. 6, 6). 



Fig. XLVI. 





Fig. XLVI. MAGNIFIED VIEW OP A PERPENDICULAR SECTION THROUGH THE EXTERNAL 

 TABLE OP A HUMAN PARIETAL BONE, DECALCIFIED. 



At a, perforating fibres in their natural situation ; at 6, others drawn out by separa- 

 tion of the lamellae ; at c, the holes or sockets out of which they have been drawn (H. 

 Muller). 



These perforating fibres, since first noticed by me, have been shown by Kolliker to 

 exist very generally in the bones of fishes, and to a certain extent in those of 

 amphibia.* 1 had myself found them abundant in the turtle, and had no doubt of their 

 general existence in vertebrata. The late lamented Henry Miiller, of Wiirzburg, has 

 supplied many details respecting their arrangement in man and mammalia, f Kolliker 

 considers them, to be connected with the periosteum, and this, no doubt, is the case 

 with some of them some of those, for example, which penetrate the external table of 

 the cranial bones ; but in cross sections of cylindrical bones they often appear to spring, 

 with their broad ends, from the deeper lamellae, and taper outwards into fine points, 

 which do not reach the periosteum ; although without doubt they must, like the bony 

 layers in which they occur, have been formed by subperiosteal ossification. They are 



* Wurzburger Naturw. Zeitschr. vol. i. p. 306. f Ibid, vol. i. p. 296. 



