THE OSSEOUS SYSTEM. 301 



ligaments, in the new-boi*n cliild, consists of a substance very nearly 

 allied to that of "colloid" (Wurzb. " Verhandl," II. 283). The liga- 

 ments have the same chemical composition as the tendons. 



§ 98. Vessels of the Bones and their accessory Organs. — A. Blood- 

 vessels. The periosteum, besides the numerous vessels passing to the 

 bone by which it is traversed, presents in its outer layer, composed of 

 connective tissue, a tolerably close network of minute capillaries (0-005 

 of a line). The blood-vessels of the hone itself are very numerous, as 

 may be seen in injected specimens, and also in recent bone full of blood. 

 In the long bones, the marrow and the spongy substance of the articular 

 ends are supplied by particular vessels, as is also the compact substance 

 of the shaft. The former, or vasa nutritia, enter the bone through large 

 special canals, one or two of which are found in the diaphijses, and 

 many in the apophyses. These vessels, with the exception of a few 

 twigs given off to the innermost Haversian canals of the compact sub- 

 stance, and which possess all the tunics proper to the vessels elsewhere 

 (even to the muscular), ramify in the marrow, where they form a true 

 capillary plexus — the vessels in which vary in size from 0-00-4 to 0'0052 

 of a line. The vessels of the compact substance arise, in great part, 

 from those of the periosteum, very soon lose the muscular coat, and 

 form, in the Haversian canals, which they either occupy by themselves, 

 or together with some medullary substance, a network of wide canals, 

 which from their structure, can only in the most trifling extent be re- 

 ferred to the capillary system, most of them possessing a layer of con- 

 nective tissue and an epithelium, and as it is only in the larger canals 

 that fine capillaries co-exist with the main vessel. The venous blood is 

 returned from all the long bones, in three ways : — 1, by a large vein 

 accompanying the nutritious artery, the ramifications of which it fol- 

 lows ; 2, by numerous large and small veins at the articular extremities ; 

 and, 3, lastly, by many small veins, which arise independently of each 

 other from the compact substance of the diaphyses, in which their roots, 

 as is correctly stated by Todd and Bowman, occupy the wider spaces 

 and sinuses, or pouch-like excavations, which are very evident even in 

 sections of bone. 



 All the vessels of bone, — the medullary vessels of the apopliyses and 

 of the diaphyses, as well as the vessels of the compact substance, — 

 communicate in a multiplicity of ways, so that the vascular system 

 throughout the entire bone constitutes a continuous whole, in which it 

 is possible for the blood from any one part to reach every other part ; 

 for it was observed by Bichat (" Anat. Gen(jral.," 1812, III. p. 37), in 

 an injected tibia, the nutritious artery of which was obliterated, that 

 the bifurcation of the vessel in the medullary canal was well injected, 

 and that the nutrition of the marrow was evidently unafl'ected. 



