GENERAL ANATOMY OF BONE. 37 



A transverse section of compact bone sometimes exhibits certain vacuities or 

 spaces, termed, by Messrs. Tomes and De Morgan, Haversian spaces. These 

 spaces are found at al\ periods of life, but especially in young and growing bones. 

 They are characterized by an irregular or jagged outline, and are apparently 

 produced by the absorption of parts of several Haversian systems, which have 

 been, to a greater or less extent, removed in order to form them. These spaces 

 may exist in various conditions: in some, the process of absorption is evidently 

 going on; in others, the spaces are linsd by newly-formed lamellae which fill 

 up the peripheral portion of the space; in others, the lamellae fill in the whole 

 of the space, leaving a Haversian canal in the centre. It would thus appear, 

 that portions of the Haversian systems are, from time to time, removed by 

 absorption, and a new system of lamellse re-formed in place of those previously 

 existing. Sometimes, these spaces may be seen filled in, at one part, by the 

 deposition of lamellae ; while, at another part, they are extending themselves by 

 absorption. 



"We have already said, that the dark spots seen in and between the lamellae, 

 arranged in concentric circles around the Haversian canals, are the lacunae. 

 They are minute cavities existing in the osseous substance, having numerous fine 

 ^ tubes called canaliculi issuing from all parts of their circumference. In fresh 

 bones, each lacuna contains a delicate cell, with pellucid contents, and a single 

 nucleus ; and from the cell numerous fine processes are given offj which fill the 

 canaliculi. These are the bone cells, discovered by Virchow. The lacunae are 

 oval flattened spaces, lying parallel to the direction of the lamellae. The canaliculi 

 issuing from them are extremely minute, their diameter ranging from Tiijijtf to 

 Sffoon of an inch. They communicate freely with the canaliculi of adjoining 

 lacunas, some opening into the Haversian canals, or in the cancelli of the spongy 

 substance, and some upon the free surface of the bone. By this communication 

 between the lacunae and canaliculi traversing the entire substance of the bone, 

 the plasma of the blood is carried into every part. 



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, which ramify 

 in a fibrous membrane termed the periosteum, which covers the surface of the bone 

 in nearly every part. From this membrane, vessels pass through 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 greater number, and these are the largest of them, 

 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 nutritious foramen 

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

 compact substance. This vessel, usually accompanied by one or two veins, sends 

 branches upwards and downwards, to supply the medullary membrane, which 

 lines the central cavity and the adjoining 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 centre of the bone, vessels which correspond 

 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; 3. 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 which are constructed 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, 



