BLOOD, NORMAL ANATOMY. 



433 



cellular texture no one denies. In the next 

 place he endeavours to establish its reticular 

 texture; 1st, by observations and experiments 

 on the bones of a chick, made during its 

 growth ; 2d, by treating bones with dilute 

 muriatic acid, and then putting them in oil of 

 turpentine to render them transparent. In every 

 bone, he says, the net-work was conspicuous. 

 He observed the same in rickets, in exostosis, 

 and in callus; and still more remarkably in the 

 bones of the amphibia, reptiles, and fishes. The 

 conclusion at which Bichat arrived is not very 

 different : " Ces lames osseuses ne me paroissent 

 point exister dans la nature.'' " Considerons 

 le tissu compact comme un assemblage de 

 fibres rapprochees mais nullement separees 

 par couche."* Blumenbach and Meckel in- 

 cline to the lamellar arrangement. More re- 

 cently bone has been submitted to microscopic 

 examination by Mr. Howship, who agrees with 

 Scarpa that the ultimate texture of bone is not 

 lamellated but reticular. He coincides, too, 

 in opinion with Havers and Leuwenhoeck as to 

 the existence of minute longitudinal canals in 

 it; and he adds that the canals communicate 

 freely with each other, and that a fine vascular 

 membrane lines them in the foetus, where they 

 may be seen projecting into the temporary car- 

 tilage during the growth of bone in the form 

 of fibres which are tubular.f Bostock says, 

 " the membrane of bone is composed of plates 

 very similar in their general form to those of 

 the cellular texture, and it is probable that the 

 earthy matter is inserted between these plates, 

 and thus is likewise disposed to assume the 

 laminated structure." And again : " As we 

 may presume that the earthy part of the bone 

 is moulded into its appropriate form by the 

 membrane into which it is deposited, we may 

 judge of the structure of the latter by that of 

 the former, which, from its firmer consistence, 

 it is more easy to ascertain. Now, whether we 

 examine bone during its formation in the fcetal 

 state, or after it has had its membrane destroyed 

 by the action of fire, we find the earth to 

 assume the appearance of fibres, which, when 

 the bone is perfected, have a tendency to a 

 laminated arrangement."! 



It is plain, from the quotations wo have 

 made from some of the most distinguished 

 writers on the structure of bone, that all before 

 the time of Scarpa considered it laminated, or 

 fibrous and laminated, while all, after his 

 publication, looked upon it as cellular. In 

 the former, however, we see some intimations 

 of a reticular texture ; in the latter we hear of 

 a tendency or a disposition to a laminated ar- 

 rangement. If, with these opinions before us, 

 we come to examine for ourselves, I think we 

 shall have no hesitation in agreeing with Scarpa 

 that it is cellular. At the same time it must 

 be confessed that the sides of the cells are, in 

 the compact tissue, so pressed together that 

 the appearance of laminse is often very striking, 



* Anat. Gencr. tome iii. pp. 24-6. Par. 1812. 

 t Medico-Chirurjiical Trans, vols. vi. and'vii. 

 \ Bostock's Elementary System of Physiology, 

 vol. i. 



VOL. I. 



and, again, that the sides of the cells have, in 

 most places, the appearance of fibres. When 

 the earthy portion is removed by an acid, we 

 can teaze out the membranous portion with a 

 pin, and almost demonstrate the fibres. But a 

 closer examination will show that we have torn 

 the cells and destroyed the true texture. The 

 laminated disposition supposed to be shown by 

 exfoliation, the weather, burning, &c. may all 

 be proved to be deceptive; and, indeed, there 

 seldom can be exhibited a plate, however small, 

 of equal thickness throughout, which has been 

 removed by any of these agents. There is, 

 however, an approach to the laminated ar- 

 rangement, and every cell is formed of parti- 

 cles which approach to the form of fibres. The 

 longitudinal canals of Havers, Leuwenhoeck, 

 and Howship, probably result from the flattened 

 cells, and may be deceptive appearances in 

 the old bone, or the channels for bloodvessels, 

 &c. 



2. The periosteum and medulla, and the 

 organization of bone as a part of the living 

 si/stew. 



A. The periosteum is a fibrous membrane 

 of a dull white colour. It covers bone on 

 every part of its circumference, except where 

 enamel takes its place as on the teeth, or car- 

 tilage as on the articular extremities, or fibro- 

 cartilage as where tendons play, or tendon as 

 on sesamoid bones. The fibres which compose 

 it run in different directions and form a tissue 

 of great strength. On the long bones the 

 greater number of fibres take a longitudinal 

 direction. The superficial ones extend for a 

 considerable length without interruption ; the 

 deep are short. All interlace with the liga- 

 ments of the articulations, and become in- 

 separably united to them, but there is not, 

 as was formerly imagined, a continuity of 

 fibres from one bone to the other by means of 

 the ligaments; on the contrary, the direction 

 of the fibres in these two organs seldom co- 

 incides. 



The external surface of the periosteum is in 

 contact with a great variety of parts : muscles, 

 synovial bursne, mucous membranes, vessels 

 and nerves, rest on it immediately, or are 

 separated from it by cellular tissue, and thus 

 permitted to move freely on it. The other 

 surface is connected to the bone by vessels, 

 and by numerous prolongations which pass 

 into the osseous substance and are lost there. 

 This connexion is weak in early life, and espe- 

 cially in the centre of the long bones ; but in 

 the more advanced periods the deeper sub- 

 stance of this membrane becomes identified 

 with that of the osseous tissue ; thus its union 

 is rendered more intimate, its thickness di- 

 minished and its density increased. The union 

 is so close in old age and even in middle life, 

 that the inner fibres of the periosteum are sup- 

 posed to be the seat of calcareous deposition, 

 and to be converted into bone. 



The vascularity of the periosteum may be 

 easily shown by injection, especially in the 

 young. Its vessels freely anastomose with 

 those of the surrounding soft parts, and there 

 is no point of the external osseous surface 



2 r 



