OSSEOUS TISSUE. 



849 



fused state of the specimen, a little dilute 

 muriatic acid should be placed upon the glass 

 in contact with the specimen. Solution of the 

 powdered mass will instantly commence, but 

 the broken granules will have disappeared be- 

 fore the entire ones are appreciably affected. If 

 at this point of the experiment the acid be re- 

 moved and replaced by pure water, a perfect 

 specimen will be gained. In examining the 

 tissue under consideration it is most satisfactory 

 to watch the action of the acid upon the cal- 

 cined or steamed bone, and especially its action 

 upon the small masses, for in these, when un- 

 dergoing the action of dilute acid, the granules 

 composing them become particularly distinct, 

 so that their individual character may be stu- 

 died ; and if the solvent be not removed, their 

 separate disappearance may be watched as the 

 superficial ones are exposed and acted upon by 

 the solvent fluid. If the acid be left with the 

 so treated bone for a sufficient length of time, 

 all the earthy matter will be dissolved and there 

 will remain a transparent indistinctly cellular 

 mass, which may be supposed to be an inter- 

 granular substance, the purpose of which was 

 to unite the granules into a compact whole. 



Bone which has been treated with dilute 

 acid without the previous removal of the ani- 

 mal matter, soon loses the earthy component, 

 leaving only the animal. This, however, does 

 not tend to develope the granularity; indeed 

 it seems, in most cases, to render it less dis- 

 tinct than in either the unaltered or the calcined 

 bone. The granules themselves are subject to 

 some variety in size, commonly varying from 

 the one-sixth to one-third the size of a human 

 blood globule. 



Of the lamina:. The form taken by the 

 bone substance is that of laminae, and these 

 laminae have a definite arrangement, so much 

 so that three distinct systems may be recognised, 

 namely, laminae of the Haversian canals ; 

 secondly, the laminae which connect the 

 Haversian systems; and thirdly, the lamina 

 which form the surface of the bone and enclose 

 the two previous orders. 



The laminae of the Haversian canals have a 

 concentric arrangement, and present, when 

 divided transversely, a series of more or less 

 distinct and perfect rings : see figs. 448 and 450. 

 They are subject to considerable variety in 

 number, but the more common amount is ten or 

 twelve. Of these, the internal lamina, that which 

 forms the parietes of the Haversian canal, is most 

 distinctly marked, while each succeeding one as 

 you proceed outwards becomes less distinct. The 

 concentric laminae with bone cells and central 

 canal have received the name of Haversian 

 system from Dr. Todd and Mr. Bowman in 

 their work on Physiology. 



Connecting these Haversian systems is a 

 second series of laminae, without which the 

 former would exist but as a bundle of loose 

 tubes. (See/g. 448, c). 



In this substance we find the laminated 

 arrangement less distinct, far less regular, and 

 the laminae individually subject to great 

 irregularity of thickness. It is often also more 

 transparent than either the Haversian or exter- 



VOL. III. 



nal system. Bone cells contained in it are 

 also more irregular in shape than those found 

 in other situations. The last division consists 

 of those laminae which surround the exterior of 

 the bone. These have greater individual 

 extent, but are the least numerous. They are 

 continuous with the laminae of the Haversian 

 system whenever the latter arrive at the surface 

 of the bone ; the external laminae in this case 

 being continuous with the inner lamina of the 

 Haversian system. 



Some authors have doubted the existence of 

 a laminated arrangement in bone. If, however, 

 young bone be examined, all doubt upon the 

 subject will be dispelled, and especially if it 

 be first macerated in weak muriatic acid, when 

 the appearance represented in Jig. 450 will be 

 seen. In bone so treated the laminae may witli 



Fig. 450. 



The lamincB as they appear after the removal of the 

 animal matter by the action of add. 



the assistance of two needles be separated. In 

 the bones of old animals the laminae are much 

 less distinct ; in these, however, they may be de- 

 monstrated if acid be used. Though the external 

 lamina is very distinct, and therefore the boun- 

 dary of each Haversian system, yet in bone of 

 advanced age the distinctness is lost in com- 

 mon with the definite outlines of the three 

 orders of laminae. The cancelli of the can- 

 cellous portion of bones are but enlarged 

 Haversian canals, which in addition to vessels 

 contain fat; the laminae therefore which form 

 the walls are those of the Haversian system. 



In connection with this division of the sub- 

 ject, the effect of madder given to an animal 

 with its food upon the osseous system may be 

 noticed, since the colour is imparted to the 

 lamince. By the taking of madder into the 

 stomach the effect of giving a deep red tinge is 

 very soon observable. In a pigeon the bones 

 were rendered brilliantly red in twenty-four 

 hours. In a young pig a similar effect was 

 produced in three weeks. 



On making sections of bone so affected the 

 colour is found to be present in the external 

 laminae of the bone, and in the inner laminae of 

 the Haversian system, thereby proving that the 

 action of colouring takes place upon those sur- 

 faces which lie in contact with vessels. This 

 fact, with many others in this article, was men- 

 tioned in a paper by the author read before 

 the Royal Society in June of 1838. 



Of the Hctversian ennuis. These canals 



3 i 



