THE PATHOLOGICAL ANATOMY 



277 



stroma may show hyaline transformation. As a rule this series of changes 

 is associated with a considerable lessening of the size of the gland and 

 always with a marked increase in the iodin store. Miiller, L. R. 



Exhaustion Atrophy. ^Brief mention may be made of atrophies 

 at this time because of the necessary physiological connection between 

 the hyperactive and the exhaustive stages, though this will be more fully 

 described under "Atrophies." While involution or recovery is the 

 usual mode of termination of active hyperplasias of whatever clinical 

 association and ex- 

 haustion atrophy the 

 rare and unusual, it 

 is 'of as great impor- 

 tance for the proper 

 appreciation of the 

 cycle of cell changes. 

 Exhaustion atrophy 

 is frequently seen in 

 the marked hyper- 

 plasias of young ani- 

 mals and of children 

 with myxedema and 

 in the late stages of 

 exophthalmic goiter. 

 If hyperplasia and 

 hyperactivity are al- 

 lowed to continue 

 without periods of 

 physiological cell rest, the cells sooner or later die of exhaustion. The most 

 characteristic morphological changes occur in the epithelium of the alveoli 

 and in the stroma. At first the stroma is probably only relatively increased, 

 but later there may be an absolute increase. The epithelial cells are in the 

 early stages of the process high columnar in type, with here and there 

 an atypical cell mass. As the atrophy progresses the epithelial cells 

 become more variable in size, shape and staining reactions. The cells 

 lose their uniform arrangement in the alveoli and piling up, desquama- 

 tion and disintegration may be seen in the same alveolus with mitotic 

 figures. All the cells of a given alveolus are not uniformly involved. 

 The nuclei of involved cells show great irregularity, sometimes en- 

 larged and hyperchromatic and always variable in size, shape and stain- 

 ing intensity. The colloid is markedly reduced or absent. As the atrophic 

 process continues the alveoli are further reduced in size by cell death and 

 advancing sclerosis until they may appear as compressed nests of cells with- 

 out the outlines of alveoli. This change has been mistaken for carcinoma. 

 Ewald, O. (a), Kocher, T. (i), Lewis, Meroz-Tydman. 





Fig. 12. More advanced active hyperplasia, thyroid of 

 common fowl (Gallus domesticus) showing greater infold- 

 ings and variations in size of alveoli. 



