BONE, NORMAL ANATOMY. 



435 



membrane. The artery is erroneously called 

 the nutritious vessel of the bone. It is ob- 

 viously intended for the marrow. A vein is 

 seen to accompany it ; and nerves may also be 

 demonstrated. 



The medullary membrane is possessed of 

 sensibility. This was long ago shown by Du- 

 verney.* According to Bicliat it enjoys a very 

 high degree of sensibility in the centre, but 

 much less towards the ends. Anatomists do 

 not agree with him in this observation, nor is 

 it found very sensible in any part. Patients 

 seldom complain of pain when, in amputations, 

 it is rudely lacerated by the teeth of the saw ; 

 but sometimes they do complain loudly, and 

 in those cases especially where the operation 

 is performed below the entrance of the nerve ; 

 in the opposite case the nerve is probably di- 

 vided with the soft parts, and the sensibility, 

 of course, destroyed. 



The marrow and the medullary canal vary 

 much in different periods of life, and under 

 different circumstances. No medullary cavity 

 exists in the cartilage which precedes bone ; 

 but Bichat asserts that the membrane is pre- 

 sent, filled with gelatine of the same ap- 

 pearance as the rest of the cartilage. An 

 assertion so improbable a priori, and so con- 

 trary to all observation, seemed to require some 

 proof to support it, yet he offers none. When 

 a cavity is formed at a later period, it is at first 

 occupied entirely by the artery ; a membrane 

 soon shows itself which contains a reddish 

 watery substance, of a gelatinous appearance, 

 not fatty : it may be dried away before the 

 fire and will not stain paper. To this the true 

 marrow succeeds, more unctuous and more 

 abundant as the individual advances in years. 

 In subjects, however, which have been wasted 

 by slow disease, and in the very aged, the 

 marrow again becomes watery, though not so 

 red as in the foetus. In the cells of the verte- 

 brae there never is well-formed marrow. It 

 there remains through life sanguineous and 

 almost destitute of oil. 



The use of the medullary membrane seems 

 to be to act as an internal periosteum, or a bed 

 in which the vessels may ramify before they 

 enter the osseous substance. Its destruction 

 to any extent is followed by the death of the 

 bone. But is the adeps contained in it of any 

 use ? Doubtless it is to the general system a 

 store of nutriment, which is absorbed, in cases 

 of wasting or marasmus, for the general good ; 

 but to the bone itself perhaps it is of no more 

 use than so much of any other soft animal 

 substance would be it fills a space which in the 

 mechanism of the bone was not to be occupied 

 with calcareous matter. Marrow was lighter 

 than the heavy earth of bone, and could at 

 any time be used for the necessities of the 

 animal. We see young bones filled with a 

 gelatinous fluid, and in birds air takes its 

 place a proof that marrow is no wise essen- 

 tial to the existence of the osseous system. 

 Various other uses have been assigned to the 

 marrow, which will not bear examination. 



Blumenbach, Haller, and their predecessors 

 conceived that it rendered bones more flexible; 

 but the bones of children, which have little or 

 no marrow, are much more flexible than those 

 of adults. Burning a bone renders it brittle, 

 and this was said to be owing to the destruc- 

 tion of its oily part ; but it is occasioned, 

 clearly, by the destruction of all its animal 

 ingredients. Some were of opinion that it 

 contributed essentially to the growth and nu- 

 trition of bone and to its union when fractured, 

 but bones are far advanced in growth before 

 it appears at all, and they unite faster in 

 the young than in the old. They unite also 

 readily in birds. Others looked on it as the 

 source of synovia ; but the very same objec- 

 tions hold to that supposition, and indeed the 

 two fluids are quite dissimilar. 



According to the law of development, so 

 generally observed, we find fishes and amphi- 

 bia, like the human foetus, for the most part 

 destitute of a medullary canal. The crocodile 

 and other lizards are, however, exceptions. 

 Some of these have considerable cavities. 

 Birds, when young, have an imperfect medulla 

 in all their bones, but at a later period the 

 canal in many of them becomes remarkably 

 developed, and then no longer contains mar- 

 row ; air takes its place, and fulfils important 

 offices in the economy of the class. In mam- 

 malia the internal structure coincides with that 

 of the human bones, except in those species 

 which have fins. These approximate to fishes, 

 and either contain no cavity or a very small 

 one filled with fluid oil. The medulla of car- 

 nivorous animals generally is softer than that 

 of herbivorous. 



Organization of bone as a part of the living 

 system. The physical properties of bone are 

 so very peculiar that we cannot much wonder 

 at the mistakes of the ancient anatomists re- 

 specting its organization. Some classed it 

 it amongst the bloodless organs ; others even 

 supposed it to be destitute of vitality; and 

 superficial observation might countenance the 

 supposition, for no pain is excited by sawing, 

 scraping, or cauterizing a bone ; but experi- 

 ment and observation, analogy and disease, 

 all convince us that it possesses well-developed 

 systems of arteries, veins, nerves, and most 

 probably lymphatics, not differing essentially 

 from those of the soft parts. These are ob- 

 scured by the presence of calcareous matter, 

 not obliterated. " Scrape a bone, and its ves- 

 sels bleed ; cut or bore a bone, and its granu- 

 lations sprout up ; break a bone, and it will 

 heal ; or cut a piece away, and more bone will 

 readily be produced ; hurt it in any way, and it 

 inflames ; burn it, and it dies ; take any proof 

 of sensibility but the mere feeling of pain, 

 and it will answer to the proof."* Animal sen- 

 sibility was unnecessary, it would even be incon- 

 venient ; it is, therefore, riot to be found, ex- 

 cept in diseased bone, where it sometimes 

 exhibits itself too acutely. 



The presence of bloodvessels may be shown 

 in various ways. l.->t. The colour of heaUhy 



Memoires de 1'Acad. dcs Sc. 1700. 



1'rli's Anat'iiny. 



2 r 2 



