CYTOMORPHOSIS. 17 



old age, but they remain active throughout life; if destroyed, they can 

 never be replaced. In many glands, in the blood and in the skin, however, 

 the cells are constantly dying and new ones are being differentiated. In 

 a few organs the cells perish, but no new ones form, so that the organ to 

 which they belong atrophies. Thus the mesonephros (Wolffian body) 

 largely disappears during fetal life; the thymus becomes vestigial in the 

 adult; and the ovary in later years loses its chief function through the 

 degeneration of its cells. 



The optical effects of regression cannot at present be properly classi- 

 fied. In a characteristic form, known as "cloudy swelling," the cell en- 

 larges, becoming pale and opaque. In another form the cell shrinks and 

 stains deeply, becoming either irregularly granular or homogeneous and 

 hyaline. The nucleus may disappear as if in solution (karyolysis, chromato- 

 lysis), or it may fragment and be scattered through the protoplasm (karyo- 

 rhexis). If the process of degeneration is slow, the cell may divide by 

 amitosis. It may be able to receive nutriment which it cannot assimilate, 

 and thus its protoplasm may be infiltrated with fat and appear vacuolated. 

 It may form abnormal intercellular substances, for example, amyloid, or 

 the existing intercellular substances may become changed to mucoid 

 masses or have lime salts deposited in them. In short, together with 

 optical changes in the cell substance there is often an impairment or 

 perversion of function. 



The removal of dead cells is accomplished in several ways. Those 

 near the external or internal surfaces of the body are usually shed or des- 

 quamated, and such cells may be found in the saliva and urine. Those 

 which are within the body may be dissolved by chemical action or devoured 

 by phagocytes. 



Every specimen of human tissue exhibits some phase of cytomorphosis. 

 In some sections a series of cells may be observed from those but slightly 

 differentiated, to the dead in process of removal. Because of the similarity 

 and possible identity of this normal, "physiological" regression, with that 

 found in diseased tissues, such specimens should be studied with particular 

 care. 



