338 THE TISSUES. 



that it is possible for the blood of any one part to reach any other 

 part. 



In the short bones, the bloodvessels present very nearly the same 

 conditions as those of the epiphyses of the long bones ; the arteries 

 and veins of larger and smaller size entering and quitting the bone 

 at numerous points on the surface. 



In the flat bones, as the scapula and coxal bone, there are distinct 

 apertures for the larger arteries and veins ; the compact substance 

 receiving finer vessels from the periosteum, and the cancellated 

 structure being supplied by numerous and large vessels. In the 

 flat cranial bones the arteries mostly enter the compact and the 

 spongy portions (diploe) from both surfaces ; while the veins have 

 only their extremities free in the cavities of the diploe as in other 

 bones, and their trunks contained in large, arborescent canals, 

 emerge at definite points through large apertures (emissaria Santo- 

 rini), and communicate freely with the veins of the dura mater. 

 The veins of the cranial bones, however, become obliterated as age 

 advances, coincidently with the diminution of the diploe. In the 

 new-born infant, arteries as well as veins, occupy the emissaria. 

 The articular cartilages have no vessels at all. Those of the syno- 

 vial membranes will be described further on. 



Lymphatic vessels in lone have been described by some anatomists. 

 Kolliker, however, does not admit their existence in either bone, 

 periosteum, or synovial membranes; though they pretty certainly 

 exist in the loose areolar tissue around the last, especially at the 

 knee. 



3. Nerves of the Bones. 



It is necessary to distinguish the nerves of the bones from those 

 of the periosteum, in which the former lie, before entering the sub- 

 stance of the bone. The nerves of the bone are larger than those 

 of the periosteum, and sometimes give off the latter as branches. 

 They exist in all bones except, perhaps, the small bones of the ear, 

 and the sesamoid bones though not in all bones fulfilling the same 

 conditions. In the large cylindrical bones, they,^?^, penetrate into 

 the medullary cavity with the nutrient vessels of the marrow (whe- 

 ther there be one or two); the trunks being visible to the naked 

 eye, and as much as ^ of an inch in diameter. They are distri- 

 buted to the marrow, following the course of the vessels, though 

 not always in apposition with them, towards the epiphyses; forming 



