294 FRANCIS A. HULST. 



Only rarely do the proliferated epithelial cells become phagocytic 

 and then they are of a low, undifferentiated type ; they are the 

 flat cells which resemble the endothelial cells and probably per- 

 form much the same function. The epithelial cells lining the 

 alveoli of the lungs and of Bowman's capsule of the glomeruli of 

 the kidney may proliferate in certain inflammatory processes and 

 the resulting cells take up a phagocytic function. 1 This would 

 seem to suggest the probable origin of phagocytes and their 

 relation to the muscular destruction in Cnlex. They arise from 

 a proliferation of mesodermic cells, appear after the degeneration 

 has become established and have no causative relation to the 

 degeneration. 



Another point which should be mentioned, although not found 

 in Culcx, is that of the myoclasts described by some observers. 

 Metschnikoff ('83) describes muscular phagocytes in the resorp- 

 tion of the tail of tadpoles, as noted in a preceding paragraph. 

 In Musca, Bruyne ('98) also finds instances of the same phe- 

 nomenon and terms these cells myoclasts. In these instances 

 there are the same initial phenomena as described in the begin- 

 ning degeneration. The nuclei, however, do not disappear after 

 hypertrophy, but persist and become surrounded by sarcoplasm. 

 This then becomes an amoeboid cell and acts as a phagocyte. 

 These myoclasts become very large when distended with numer- 

 ous sarcolytes. In such a case we have cells arising from the 

 degenerating tissue which attacks tissues of similar origin. The 

 muscles having come to an end of their usefulness, produce the 

 agents of their own destruction. In the study of Citlex the 

 behavior of the nuclei as above described was constant, /. i\, both 

 nuclei and sarcolytes are eventually consumed together in the 

 body cavity. Nothing that corresponds to the description of 

 myoclasts has been observed. 



Late in the process of metamorphosis, seen especially in ad- 

 vanced pups, but to some extent in earlier forms are masses of 

 sarcolytes or muscle fragments, some free, others enclosed in 

 phagocytes, which show various degrees of degeneration. A 

 very few retain their normal staining properties when treated 



'"Proliferation and Phagocytosis," F. B. Mallory. From The Jour. Exper. 

 Meet., Vol. V., No. i, 1900, p. 7. 



