396 RETROGRESSIVE CHANGES 



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. In the 

 muscle tissue of salmon migrating to the spawning grounds occurs one 

 of the most marked examples of atrophy, and Greene^^ has found that 

 at least 30 per cent, of the protein lost from the muscles may be con- 

 sidered as stored protein, since it can be lost without injury to the 

 muscle. 



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 Wakeman®^ 

 found a decrease in solids, and a lowered proportion of diamine acids. 



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

 mechanism involved in atrophy, using especially the involuting tail 

 of the tadpole as his test object.''^ He beheves that autolysis is the 

 primary factor, probably induced by acidity that results from vascular 

 occlusion. 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 quantitatively in the 

 urine.''* Bradley" calls attention to the fact that atrophy occurs 

 commonly under conditions of reduced blood supply, which implies 

 partial asphyxia and a resulting tendency to local excess of H-ions, 

 which would favor autolysis. Conversely, hypertrophy is observed 

 with abundant blood supply which tends to keep the reaction of the 

 tissues so low in H-ions that autolysis is held at a minimum. 



CLOUDY SWELLING'6 



The characteristic appearance of organs the seat of cloudy swell- 

 ing, which is frequently likened to a "scalded" appearance, sug- 



69 Jour. Biol. Chem., 1919 (39), 435. 



'"> Carnegie Inst. Publ., 1915, No. 203. 



" Cesa-Bianchi, Frankf. Zeit. Path., 1909 (3), 723. 



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



" Biol. Bull., 1918 (34), 149. 



''* Hlemons, Bull. Johns Hopkins Hosp., 1914 (25), 195. 



"^ Jour. Biol. Choin 1910 (25), 201. 



" Review of general features by Landsteiner, Ziegler's Beitr., 1903 (33), 237. 



