SECT. 98.] OSSEOUS SYSTEM. 1 85 



small veins, which arise independently from the compact substance 

 of the shaft, in which their roots, as Todd and Bowman correctly 

 pointed out, occupy the wider spaces and the sinus or pouch-like 

 excavations, as may he well seen in polished sections of the bones. 

 All the vessels, both the medullary vessels of the apophyses and 

 diaphyses, and the vessels of the compact substance, communicate 

 in various ways, so that the vascular system forms one continuous 

 whole throughout the entire bone, and the blood is enabled, pos- 

 sibly, to flow from any one part to all the others. Bichat ac- 

 cordingly (iii. 44), found, the medulla very well injected in an in- 

 jected tibia, the nutrient arteries of which were obliterated. 



In the short hones, the blood-vessels present the same relations 

 as in the apophyses of the long ones. This is also the case with 

 t\\Q flat hones; only the scapula and innominate bone possess special 

 nutrient foramina for larger arteries and veins, and in all cases their 

 compact substance receives its finer vessels from the periosteum. 

 In the flat cranial bones, the veins, or vena diploetica, have only 

 their roots free in the marrow, as in other bones ; their trunks, 

 branches, and larger ramifications, on the other hand, run sepa- 

 rately, mostly, without being accompanied by medulla, in special, 

 arborescent larger canals, the so-called Breschet's bone-canals, 

 which terminate at fixed places by large apertures (emissoria 

 Santorini). With regard to the vessels of the cartilages of the 

 osseous system, and of the synovial membranes, see §§94 and 95. 



B. Lymphatic vessels have been observed in no part of the 

 osseous system with certainty, except in the loose areolar tissue 

 around the articular capsules, and between the latter and the 

 periosteum of the apophyses, especially at the knee-joint. 



§ 98. Nerves of the Osseous System. — The periosteum is rich in 

 nerves, and although the greater part of them are destined for the 

 subjacent bone, nevertheless, appareutly, in all bones there are 

 nerves which ramify in the membrane, occasionally presenting divi- 

 sions of the primitive tubules, and terminating by free extremities. 

 These nerves are most numerous at the articular extremities of the 

 bones, especially at the knee. 



The bones themselves, Avith, perhaps, the exception of the ossi- 

 cula auditus and ossa sesamoidea, all contain a considerable number 

 of nerves. These pass into the bones partly with the nutrient 

 arteries, and ramify in the marrow, partly supply the spongy sub- 

 stance of the articular extremities of the long, short, and flat 

 bones. They are most numerous in the apophyses of the large 

 cylindrical bones, in the vertebrae, and the larger flat bones. 



