42 INANITION AND MALNUTRITION 



mens that have not been fed for several weeks before cutting: the other tissues 

 degenerate somewhat while the nervous tissue does not to nearly the same extent. 

 A specimen starved for 18 weeks showed the head ganglion nearly as large as 

 those in corresponding specimens fed during the same time, while other tissues 

 were much reduced; everything in the shape of fat or yolk material having 

 entirely disappeared, and the actual size of the animal having been reduced from 

 n X 3 mm. to 3 X M mm." 



More detailed investigation of the histological changes in planarians during 

 inanition was made by Schultz ('02, '04, '04a, '08, '08a). In his first paper, 

 Schultz ('02) noted a marked decrease in the body-size of Dendrocoelum lacteum. 

 "Bei hungernden Dendrocoelum lacteum konnte ich beobachten, dass die Seiten- 

 verzweigungen des Darmes allmahlich immer armer wurden. Auf Schnitten 

 erwies es sich, dass das Darmepithel in den Seitenzweigen von den feinsten 

 Endverzweigungen angefangen und weiter zum Centralstamme fortschreitend 

 sich aus seinem Verbande lost. So sieht man auf Durchschnitten oft das Darm- 

 lumen schwinden und die einzelnen Epithelzellen freiim Mesenchym liegen." 



The histological changes during inanition in Planaria lactea were described 

 by Schultz ('04) in greater detail. In six months the body length is reduced to 

 }{o or yi.2, and the worms begin to die after seven months. Some cells undergo 

 degeneration, terminating in necrosis; others undergo reduction, i.e., a"dediffer- 

 entiation" with return to embryonal condition; while some cells (body epithe- 

 lium) remain unchanged in size and structure. The nuclei are very resistant 

 and never decrease in size. 



The alimentary canal in general decreases in proportion to the entire body, 

 the form of the gut and branches being usually well preserved. The lining epi- 

 thelial cells early begin to show changes, with loss of granules and fat, followed 

 by progressive cytoplasmic atrophy. In some cases the cells degenerate, the 

 nuclei often undergoing hypertrophy and karyolysis. In other cases the cells 

 fuse into a syncytium with scanty cytoplasm, which may obliterate the gut 

 lumen. The eyes likewise degenerate relatively early, by the fourth or fifth 

 month, the optic cup breaking up. The pigment cells become disintegrated, 

 leaving intercellular masses of pigment granules which are later resorbed. The 

 parenchyma 1 (interstitial " Grundgewebe ") is largely resorbed by the sixth 

 month of fasting, although some cells remain unchanged. The muscles persist,, 

 even in extreme stages of inanition, but are reduced in size proportional to the 

 whole body. The muscle-cells become shorter, but retain the same thickness. 

 The nervous system is very resistant, although degeneration of nerve-cells 

 occurs. "Das Gehirn und die Nervenstamme mit ihren Quercommissuren 

 sind noch zuletzt, wenn das Tier schon dem Hungertode ganz nahe ist, gut 

 entwickelt." The reproductive system varies in its different parts. Reduc- 

 tion begins relatively early in the penis, which ultimately disappears. The fate 

 of the ovaries is uncertain. The vasa deferentia, oviducts and associated genital 



1 It should be noted that many writers on the histology of invertebrates unfortunately use 

 the term " Parenchyma " in a sense quite opposite to that generally used for vertebrates, where 

 the corresponding interstitial tissue is designated as the "stroma." 



