33.2 SPECIAL HISTOLOGY. 



in the new-horn child, consists of a substance very nearly 

 allied to that of "colloid" (Wurzb. 'Verhandl./ IT, 283). The 

 ligaments 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 (0005'"). The blood-vessels of the bone 

 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 diaphyses, and many in the apophyses. These vessels, 

 with the exception of a few twigs given off to the innermost 

 Haversian canals of the compact substance, 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 O004"' 

 to O0052'". 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 referred to the capillary 

 system, most of them possessing a layer of connective 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 ramifi- 

 cations of which it follows ; 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. 



