302 THE ' SOLIDS. 



sian canals, and ramifying through these form a capillary 

 network ; these external periosteal vessels may be seen with 

 the unaided eye extending into the bone like so many fine 

 threads on the cautious detachment of the periosteum. 



Again, in the long bones, a large artery penetrates by an 

 oblique canal situated at the junction of their upper and 

 middle thirds, into the medullary cavity, and sends branches 

 upwards and downwards, which ramify on the membrane of 

 the medulla or internal periosteum, some of these proceed 

 onwards into the medullary cells, and others inosculate with 

 the capillaries of the Haversian canals already referred to. 



The flat and irregular bones are furnished not with a 

 single vessel of large calibre, but with several of smaller size. 



These larger arteries are accompanied by veins, whereby a 

 portion of the venous blood is returned from the bone. 



Breschet *, moreover, has described in the flat bones, and 

 especially in those of the cranium, a system of osseous canals, 

 which contain only veins, and which are furnished with valves, 

 which is not the case with the other veins of bones. 



The walls of these canals, which ramify after the manner 

 of vessels, are pierced with apertures, by which they receive 

 small capillaries : they traverse principally the spongy por- 

 tion of bones, afterwards they pass through the compact part, 

 and finally terminate on the external surface of the bone. 



These canals are best seen in the flat bones of the cranium, 

 which should be dried, and the outer table of compact sub- 

 stance removed. 



Lymphatics have been observed in some few instances in 

 bone. 



Nerves of Bone. 



Nerves have not hitherto been satisfactorily traced into 

 bones ; nevertheless, the great pain experienced in diseased 

 conditions of them proves incontestably the existence of ner- 

 vous fibrillae. 



* N. A. N. C. xxiii. P. i. p. 361. ; Recherches Anat. Physiolog. et Pat. 

 sur le Systeme Veineux, Paris, 1829. fol. 



