46 GENERAL ANATOMY. 



Vessels of Bone. The bloodvessels of bone are very numerous. Those of the 

 compact tissue are derived from a close and dense network of vessels, ramifying 

 in the periosteum. From this membrane, vessels pass into the minute orifices 

 in the compact tissue, running through the canals which traverse its substance. 

 The cancellous tissue is supplied in a similar way, but by a less numerous set 

 of larger vessels, which, perforating the outer compact tissue, are distributed 

 to the cavities of the spongy portion of the bone. In the long bones, numerous 

 apertures may be seen at the ends near the articular surfaces, some of which 

 give passage to the arteries referred to ; but the most numerous and largest 

 apertures are for the veins of the cancellous tissue which run separately from 

 the arteries. The medullary canal in the shafts of the long bones is supplied 

 by one large artery (or sometimes more), which enters the bone at the nutrient 

 foramen (situated in most cases, near the centre of the shaft), and perforates 

 obliquely the compact substance^ This medullary or nutrient artery, usually 

 accompanied by one or two veins, sends branches upwards and downwards, to 

 supply the medullary membrane, which lines the central cavity and the adjoin- 

 ing canals. The ramifications of this vessel anastomose with the arteries both 

 of the cancellous and compact tissues. In most of the flat, and in many of the 

 short spongy bones, one or more large apertures are observed, which transmit, 

 to the central parts of the bone, vessels corresponding to the medullary arteries 

 and veins. 



The veins emerge from the long bones in three places (Kolliker). 1. By a 

 large vein which accompanies the nutrient artery ; 2. By numerous large and 

 small veins at the articular extremities ; 8. By many small veins which arise 

 in the compact substance. In the flat cranial bones, the veins are large, very 

 numerous, and run in tortuous canals in the diploic tissue, the sides of the 

 canals being formed of a thin lamella of bone, perforated here and there for the 

 passage of branches from the adjacent cancelli. The veins thus inclosed and 

 supported by the osseous structure, have exceedingly thin coats ; and when 

 the bony structure is divided, they remain patulous, and do not contract in the 

 canals in which they are contained. Hence the constant occurrence of purulent 

 absorption after amputation, in those cases where the stump becomes inflamed, 

 and the cancellous tissue is infiltrated and bathed in pus. 



Lymphatic vessels have been traced, by Cruikshank, into the substance of 

 bone, but Kolliker doubts their existence. Nerves are distributed freely to 

 the periosteum, and accompany the nutrient arteries into the interior of the 

 bone. They are said, by Kolliker, to be most numerous in the articular ex- 

 tremities of the long bones, in the vertebra, and the larger flat bones. 



Minute Anatomy. The intimate structure of bone which in all essential par- 

 ticulars is identical in the compact and cancellous tissue, is most easily studied 

 in a transverse section from the compact wall of one of the long bones after 

 maceration, such as is shown in Fig. 17. The large round spaces seen in 

 the figure are the Haversian canals, and in these canals the larger vessels of the 

 bone ramify. The fine lines leading out of (or into) these canals are called 

 canaliculi, and the irregular dark spaces, which may be noticed to have a gene- 

 ral circular arrangement round the Haversian canals, are called the lacunse. 

 The canaliculi which originate in one lacuna most frequently run into a neigh- 

 boring lacuna, or else into a neighboring Haversian canal ; some of them, how- 

 ever, anastomose with others in their neighborhood, and a few appear to termi- 

 nate in blind extremities or to bend backwards. The concentric rings of lacunae 

 round each Haversian canal are called lamellae. The irregular intervals which 

 would be left by the juxtaposition of these lamellae, are seen in the figure to 

 be filled up by lacunae and canaliculi which communicate with the systems 

 composing the adjacent lamellae. The interspaces between the lacunas and 

 canaliculi are filled with a granular homogeneous solid material, the ultimate 

 mineral base of the bone. 



If a longitudinal section be taken, as in Fig. 18, the appearances are 



