REPARATIVE PROCESS. 447 



had been divided, the bones of the quiescent limb only weighed 81 grains, 

 whilst those of the exercised limb weighed 89 grains. 1 It is an important 

 fact, which was first pointed out by Mr. Paget, 2 that when fatty degeneration 

 is commencing in any tissue, which is characterized by the persistence of its 

 nuclei, it is in the nuclei that the first alterations are seen ; for they become 

 pale and indistinct, and may even disappear altogether, almost before any 

 other change is discernible in the contents of the cells or tubes to which 

 they appertain ; but in atrophy from mere decrease, this disappearance of 

 the nuclei does not occur. 



361. Separative Process. The nutritive operations take place with extra- 

 ordinary energy and rapidity in the process of Reparation; by which losses 

 of substance occasioned by injury or disease are made good. In its most 

 perfect form, this process is exactly analogous to that of the first development 

 of the corresponding parts ; and its results are as complete in the one case 

 as in the other. In fact, among the lowest tribes of Animals, we find these 

 two conditions blended, as it were, together; for the process of reparation 

 may be carried in them to such an extent, as to reproduce the whole organ- 

 ism from a very small portion of it. In the Hydra, or Fresh-water Polyp, 

 there would seem to be scarcely any limit to its power; for, even if the body 

 of the animal be minced into small fragments, every one of these can pro- 

 duce a new and perfect being. In this manner, no less than forty have been 

 artificially generated from a single individual. In ascending the Animal 

 scale, we find this reparative power less conspicuous, because limited in its 

 exercise to particular tissues and to comparatively insignificant parts of the 

 body; 3 and in Man, as in other warm-blooded Vertebrata, the regenerative 

 power is for the most part restricted in its exercise, as Mr. Paget has pointed 

 out, 4 to three classes of parts, namely : (1.) "Those which are formed en- 

 tirely by nutritive repetition, like the blood and epithelia (their germs being 

 continually generated de novo in the ordinary condition of the body); (2.) 

 Those which are of lowest organization, and (what seems of more impor- 

 tance) of lowest chemical character, as the gelatinous tissues, the areolar 

 and tendinous, and the bones; (3.) Those which are inserted in other tissues, 

 not as essential to their structure, but as accessories, as connecting or incor- 

 porating them with the other structures of vegetative or animal life, such as 

 nerve-fibres or bloodvessels. With these exceptions, injuries or losses are 

 capable of no more than repair in its limited sense i. e., in the place of what 

 is lost, some lowly organized tissue is formed, which fills up the breach, and 

 suffices for the maintenance of a less perfect life."- -Yet, even thus restricted, 

 the operations of this power are frequently most remarkable ; and are in no 

 instance, perhaps, more strikingly displayed, than in the re-formation and 

 remodelling of an .entire Bone, when the original one has been destroyed by 

 disease. That this power is intimately related to that by which the organ- 

 ism is normally built up and maintained, is evident, not merely from the 

 peculiar mode in which it is exercised, its tendency being always to repro- 

 duce each part in the form and structure characteristic of it at the particular 

 period of life, and not according to its embryonic type, but also from the 

 fact, that it is more effectual in the state of growth than in the adult con- 

 dition, and that it can do far more in the embryonic state, when development as 

 well as growth is taking place, than after the developmental process has ceased. 

 In fact, as Mr. Paget has remarked (loc. cit.), its amount at different periods 

 of existence, as in different classes of animals, seems to bear an inverse ratio 



1 Physiological, Anatomical, and Pathological Researches, p. 10. 



2 Lectures on Surgical Pathology, vol. i, p. 106. 



3 See Princ. of Cornp. Phys., chap, xi, sect. 3. 4 Op. cit , p. 164. 



