ATROPHY 393 



bound to })r()teiii in imisrlcs wiiicli have atrophied after nerve section, 

 because of the jx'i-sistenee of iiuelear and loss of non-nueh'ar elements 

 (.Grund -"''), but there is little ehanjie in the i^roportion of mono- and 

 di-amino nitrogen.^^ 



ATROPHY 



The chemical chanpfes of simple atroi)liy have not, so far as I can 

 find, been definitely studied. It is to be presumed, in view of the 

 structural changes, that analysis of atrophied tissues would show a 

 relatively high nucleic acid and collagen content. It is known that in 

 atrophy the cell lipoids are not much altered, while the simi)ler fats 

 may be increased in parenchymatous organs. In fatty tissues, of 

 course, the fat is greatly reduced, its place being partly taken by 

 serum (serous atrophy of fat). In the heart muscle, especially, but 

 also to a less extent in the liver and kidney, during atrophy there is an 

 increased pigmentation (brown atrophy) apparently consisting of 

 lipochromes or lipofuscins ; but it is to be doubted that this represents 

 so much an actual increase in pigment as a relative increase through 

 loss of other cellular elements. Atrophied tissues also tend to undergo 

 a marked compensatory invasion by fatty areolar tissue if located in 

 contact with such tissue ; e. g., atrophy of muscles after nerve section, 

 specific muscular dystrophies, and atrophy of the pancreas. 



Starvation, of course, produces typical atrophic changes in the 

 tissues, and the general effects on metabolism have been especially 

 fully worked out by Benedict.-'*-'' The structural changes in parenchy- 

 matous cells are described ~^^ as of two types ; first, granular changes 

 and vacuolization of the cytoplasm, resembling the effects of osmotic 

 pressure alterations; second and later, lysis of cytoplasm with also 

 some involvement of the nuclei, after the order of autolytic changes. 

 The cell walls may also become indistinct, so that the cells resemble a 

 syncytium. -*'° In the atrophied muscle after nerve section Wake- 

 man ^^^ found a decrease in solids, and a lowered proportion of 

 diamino acids. 



Morse has considered, by experimental methods, the question of the 

 mechanism involved in atrophy, using especially the involuting tail 

 of the tadpole as his test object.-^® He could find no evidence that 

 autolysis is accelerated during this involution, nor in the atrophying 

 muscle after nerve section. The involution of the puerperal uterus, 

 whether it can properly be called atrophy or not, seems to be the 

 result of heightened autolysis, the products of which are excreted 



2TaArch. exp. Path., 1912 (67), .39.3. 



28Wakeman, .Tour. Biol. Chem., 190S (4), r37. 



28aCarnefrie Inst. Piihl., 1915, No. 203. 



28b Cesa-Biandii. Frankf. Zeit. Path., 1909 (3). 723. 



28cMorgulis, Howe and Hawk, Biol. Bull., 1915 (28), 397, 



28dJour. Biol. Chem., 1908 (4), 137. 



28eAmer. Jour. Physiol., 1915 (36), 145. 



