110 CARNEGIE INSTITUTION OF WASHINGTON. 



in the living tissue as in fixed preparations. This is due to the fact that 

 they were not drawn into thick bundles (fibrils), but remained spread 

 out over the surface of the cell. It would seem probable, therefore, 

 that cross-striations are laid down in the heart-muscle cell coincident- 

 ally with the differentiation of the latter. Whereas fibrils are not 

 present in living tissues, upon fixation the cross-striations are drawn 

 into fibrils and appear as sharply marked structures, varying in form 

 according to the fixative used and the method of treatment. As the 

 substance increases during development, naturally the appearance of 

 cross-striations becomes clearer the older the age studied. Any 

 attempt to formulate a theory of contraction based upon myofibrils, as 

 has been done in the past, we now know must prove unsatisfactory, at 

 least as regards the heart-muscle, since the structure upon which such 

 theories have been based is not a part of the living heart-muscle cell. 



Experiments have been made by Dr. J. R. Cash to determine the 

 effect of ether-vapor on various types of cells in tissue cultures. He 

 finds that connective-tissue cells, muscle-buds, and nerve-fibers from 

 explants of embryonic chick tissue, when exposed to ether, develop 

 within 1 to 3 minutes interesting vesicles which bulge out at points on 

 the surface of the cell. These vesicles rapidly change their shape and, 

 following sublethal amounts of ether-vapor, flow back and the cell 

 assumes its normal appearance. After slow ether death the vesicles 

 remain active, but when rapid death ensues the entire cell assumes a 

 rounded form and few if any vesicles appear. Similar changes are 

 readily produced by subjecting old cultures (3 daj^s) to markedly 

 hypotonic salt solution. Immediately (within 30 seconds) numerous 

 vesicles appear and, after characteristically changing sliape for a short 

 time, flow back into the cell. Such changes are less readily produced 

 in young, healthy cells. Similar vesicles have occasionally been noted 

 in degenerating cultures (4 to 5 days). From these observations it 

 would seem that such vesicles are evidence of degeneration by which 

 changes at points in the cell-membrane occur, allov/ing rapid imbibi- 

 tion of water. In the functionally active cell this change is probably 

 overcome by the internal metabolism of the cell. 



In connection with his studies upon hydatiform degeneration. 

 Professor A. W. Meyer made a complete examination of 61 concep- 

 tuses, both normal and pathological, for the occurrence of the so-called 

 Hofbauer plasma-cells. These cells were originally thought by Hof- 

 bauer to be characteristic of placentae from the fourth week on, and the 

 vacuoles present in them were regarded as having an assimilative and 

 digestive function. Both before and subsequent to Hofbauer there 

 have been many speculations as to the origin and significance of these 

 cells, the recent trend being toward the theory that they are mesen- 

 chyme cells in process of disintegration. Dr. Meyer finds that they are 

 especially numerous in cases of hydatiform degeneration, though it 



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