438 OP NUTRITION. 



newly-formed ganglionic vesicles taking the place of those which have un- 

 dergone disintegration. But there are other textures, whose nutrition is 

 more completely interstitial; their elements being more closely coherent, and 

 their newly-formed portions being developed throughout the substance of 

 the old, instead of (as in the case of the epidermis and its appendages) su- 

 perficially or in mere continuity with it. Such is the case, for example, with 

 Muscle, the mode of whose nutrition has not yet been elucidated. We can 

 only infer from analogy, that here too each fibre or fibril will pass, in the 

 course of its development, through the same stages which those of the em- 

 bryo did when its muscles were first formed. And this analogy seems to de- 

 rive support from the presence, in all well-nourished muscles, of bodies 

 which bear the appearance of nuclei ; for these, as Mr. Paget remarks, "are 

 not the loitering impotent remains of embryonic tissue, but gerrns or organs 

 of power for new formation." And it is further confirmatory of this view, 

 that losses of substance of muscle which involve the destruction of these 

 centres of nutrition, are not replaced, like losses of cuticle, by new tissue of 

 the same kind ; the power to form it not being inherent in the blood or in 

 the neighboring parts. Nevertheless it must be admitted that no intermedi- 

 ate stages of development can be traced in the fibres, even of those muscles 

 of the adult which are in most constant use, and of which the nutrition is 

 the most active, that are at all comparable to those which are met with in 

 the muscular tissues of the embryo. With regard, again, to the interstitial 

 nutrition of Bones and Teeth, we have no certain knowledge. That some 

 movement of nutritive fluid is continually taking place through them, is 

 made apparent by the effects of madder in gradually tinging even the bones 

 and teeth of the adult, though for such a change a much longer period is 

 required in the adult than in the young animal ; how far this movement, 

 however, is subservient to any continual change of substance, still remains 

 doubtful. If the supply of blood be withdrawn from a tooth or from a bone, 

 or even from a part of the latter, the structures thus cut off from connection 

 with the act of nutrition soon die, become detached from the living parts 

 around, and are thrown out of the body. Of this we have a very good ex- 

 ample in the annual exuviation of the antlers of the Deer, which is partly 

 brought about by the choking up of the Haversiau canals that give passage 

 to bloodvessels, with concentric osseous deposit, and partly, as Loveu, 1 Kol- 

 liker, 2 Morison, 3 and others have shown, by the absorptive power of peculiar, 

 many-nucleated giant cells (the Myeloplaques of Robin, and Riesenzellen of 

 Virchow). Something of this kind seems to be continually taking place in 

 ordinary Bone, upon a more limited scale ; individual Haversiau systems 

 being removed by absorption, leaving spaces termed the Lacuna? of Howship, 

 and being replaced by new formations of the same kind, probably during 

 its whole life, without any change in external configuration. So far as can 

 be gathered from observation, the process of interstitial decline and death 

 usually takes place too rapidly for its stages to be perceptible, and is imme- 

 diately followed, in the normal condition of the system, by the removal of 

 the effete particles ; so that it is only when this removal is from any cause 

 obstructed, as happens in the cases to be presently cited, that we see any in- 

 dication of the stages through which the disintegrating tissues pass. 



351. There is one remarkable form of degeneration, however, which is 

 common to nearly all the tissues, and which seems to occur as a normal 



1 Love^n, Wiirsburg Phys. Med. Verband., N. F., 1873, Band 4, p. 1. 



2 Kolliker, idem, p. 34. See the Memoir by Messrs. Tonics and De Morgan, On 

 tho Structure and Development of Bone, in Pbilos. Transact., 1853, p. 111. 



3 Edin. Med. Journ., Oct. 1873. 



