430 RETROGRESSIVE CHANGES 



skin (but not in the brain, where it maj^ be demonstrated chemically 

 in minute quantities). 



Glycogen is commonly said to be especially abundant in fetal tis- 

 sues, but it is not present in all fetal cells,^- nor is it always most 

 abundant in the most rapidly growing tissues. Althoug-h both fat 

 and glycogen are quite abundant in fetal muscle and liver tissues, 

 the liver of early embryos does not contain either.^^ Invertebrates 

 and the lower vertebrates have more than the higher forms. In mam- 

 malian adults the liver and muscle contain the most glycogen, carti- 

 lage standing next, and it is also present in squamous epithelium 

 (particularly the middle layers), especially that of the vagina (Wieg- 

 mann), but not in slightly stratified (cornea), transitional, or cylin- 

 drical epithelium. Normal human kidneys do not seem to show gly- 

 cogen, but it may be present in the kidneys of mice, rabbits, and 

 cats. There is considerable in the heart muscle.^* Gh^cogen is most 

 abundant in the utenis at the time of child-])irth, and is abundant in 

 the placenta ; but it is also present in the uterus and tubes independent 

 of pregnancy.^*'' After pancreas extirpation, Fichera ^^ observed a 

 disappearance of all visible glycogen, except a little in the cartilage 

 and stratified epithelium ; hence he considers the glycogen-content as a 

 function of cell nourishment. Fat and glycogen often occur together, 

 although one may be present without the other (Gierke). Presuma- 

 bly the failure to find glj^cogen in certain cells depends rather on a 

 failure of technic than on a total absence of glycogen. 



There has been some diversity of opinion as to whether glycogen 

 occurs as granules in the living cell, or whether the granules are 

 formed from a homogeneous substance by hardening fluids. In view 

 of the clear-cut, definite spaces it may leave in cells when dissolved 

 out, glycogen probably occure as granules, especially when present 

 in abnormally large quantities. The studies of Arnold have shown 

 that in many cells the glycogen takes on a definite structure, in close 

 relation to the plasmosomes. It has been suggested that the intra- 

 epithelial hyaline bodies (Russell's fuchsin bodies) are glycogenic, 

 w^hich idea is probably not correct. Habershon and others have sug- 

 gested that eosinophile granules are either glycogen or related to it. 

 The presence of glycogen in the cells seems to cause no injury to the 

 cytoplasm, and if it again disappears, the cells become quite normal.^" 



32Spp Glinko. Biol. Zoit.. Moskau. 1911 (2), 1. 



33 AdainofT (Zeit. f. Biol.. 1005 (46), 288) contests the idea that the amount 

 of frlycofren is in direct relation to <rro\vth enortry; see also !Mendel and Leaven- 

 worth (Amer. Jour. Physiol., 1007 (20), 117), who found no particular abundance 

 in the tissues of the fetal pip. 



3+Berl)linjrer, Ziealer's Beitr., 1012 (".3), 155. 



34a :McAllister, Jour. Obs. Clvn. Brit. Emp., 101.3 (34), 01. 



sr. Ziepler's Beitr.. 1004 (3fi). 273. literature. 



30 Yet Teissier (Compt. Bend. Foe. Biol.. 1000 (52), 700) I)elieves the amount 

 normally present in the liver is strongly bactericidal, and in a hater publication 

 {Hid., 1902 (54), 1098) considers that it is toxic to liver-cells. Wendelstadt 



