BONE. 61 



69). The fibres often cross one another in adjacent lamellae, and in 

 the Haversian systems they run in some lamellae concentrically, in 

 others parallel with the Haversian canal. In shreds of lamellae which 

 have been peeled off from the surface the perforating fibres may some- 

 times be seen projecting from the surface of the shred, having been 

 torn out of the deeper lamellae (fig. 69, c, c). Where tendons or liga- 

 ments are inserted into bone, their bundles of white fibres are prolonged 

 into the bone as perforating fibres. 



The lacunae are occupied by nucleated corpuscles, which send branches 

 along the canaliculi (fig. 70). 



The Haversian canals contain one or two blood-capillaries and 

 nervous filaments, besides a little connective tissue; and the larger 



Tlotenh f FlG ' 71 '- SECTION OF A HAVERSIAN CANAL, 



(Joseph.) SHOWING ITS CONTENTS. (Highly 



a, proper wall of the lacuna, where the corpuscle magnified. ) 



has shrunken away from it. ,, , . , .,, 



a, small arterial capillary vessel ; v, large venous 

 capillary; n, pale nerve-fibres cut across; Z, 



Ones may also Contain a few mar- cleft-like lymphatic vessel ; one of the cells 



forming its wall communicates by fine branches 



rOW-CellS. I here are also Clett- with the branches of a bone-corpuscle. The 



. . . , substance in which the vessels run is connec- 



llke lymphatic Spaces running With tive tissue with ramified cells ; its finely 



, , iii granular appearance is probably due to the 



the vessels and Connected through cross-section of fibrils. The canal is sur- 



,. ,. ..,11 -I f rounded by several concentric lamella?. 



canaliculi with branches from cor- 

 puscles within the neighbouring lacunae of the osseous substance 

 (fig. 71). 



The periosteum (which is studied in torn-off shreds, in preparations 

 stained in situ with silver nitrate, and in logwood-stained sections from 

 a bone which has been decalcified in chromic or picric acid) is a fibrous 

 membrane composed of two layers, the inner of which contains many 

 elastic fibres. In the outer layer numerous blood-vessels ramify and 

 send from it branches to the Haversian canals of the bone. The 

 periosteum ministers to the nutrition of the bone, partly on account of 

 the blood-vessels arid lymphatics it contains, partly, especially in young 

 animals, on account of the existence between it and the bone of a layer 



