STRUCTURE OF THE BONES. 19 



the compact portion, is sometimes seen swelled and expanded, 

 so as to develop in its substance, a cellular arrangement, 

 somewhat like that of the common spongy tissue. Maceration 

 of a bone in water, after its earthy part has been removed, 

 exhibits the same cellular structure. In fact, the principal 

 difference between these varieties of bony tissue, consists in 

 their difference of density, with some variation in the disposition 

 of their fibres ; the cells being condensed in the compact portion 

 so as to admit of a decrease in the diameter of the bones, 

 without a corresponding diminution of their strength. Hence 

 the amount of substance being the same, in the extremities and 

 shafts of the long bones, sections of equal length must of course 

 be of equal weight. — 



— In structure bone is composed of lamella;, which are con- 

 centric in long and parallel in flat bones. Between the lamellae 

 run the vascular canals of the bones, and are lodged the bony 

 corpuscles, which have been lately discovered. See p. 46. 

 — In the firmness of their texture and their general aspect, 

 bones resemble inorganic matter, but they are nevertheless 

 highly organized. 



For example, if a bone be macerated in certain acid liquors, 

 the earthy matter will be dissolved, and a membranous or 

 cartilaginous substance -will remain, resembling the bone in 

 form and size.* 



If the bones of a young subject, after being injected, be treated 

 in the same way, this membranous substance will appear to be 

 very vascular — when the injection has been successful, it will 

 appear uniformly reddened by the greatest number of vessels 

 which are filled with the matter of injection. These vessels 

 discharge blood when the periosteum is removed from the 

 surface of bones, in the living subject, and they also form 

 granulations upon bony surfaces that have been thus denuded. 



— On the other hand if a recent bone be exposed for a 

 considerable time to the action of a moderate fire, or boiled for 



* One part of muriatic acid to thirty of water is a good mixture for this 

 purpose, by taking care to keep up the strength of the mixture by additions of 

 the acid from time to time. — h. 



