CELL STRUCTURE 39 



tcristic formations wliicli recall at once the structures found in the 

 protoplasm of hardened colls. Moreover, the use of different fixing 

 agents, such as osmic acid, formalin, and bichloride of mercury, pro- 

 duces just the same differences in the structure of colloidal solutions 

 that they produce in the protoplasm of cells hardened by tliom. 

 Neither are the appearances seen in unfixed specimens reliable indi- 

 cations of the true structure of the living protoplasm. Granules of 

 secretion may disappear after or during the death of the cell (e. (j., 

 glycogen) or they may swell up (e. g., mucin granules), thus giving 

 the aj^pcarance of a network or honeycomb which is then incorrectly 

 ascribed to the protoplasm itself. Death of the cells, even when not 

 produced by external influences, seems to be accompanied by coagula- 

 tion of some parts of the cell constituents, and hence a cell examined 

 in anything but its normal living condition, an extremely difficult 

 matter, will not present a true idea of how it appears and is composed 

 while in that condition. By microdissection with the Barber pipette 

 method it is possible to study the properties of unaltered living cyto- 

 plasm, and Seifriz^" concludes from his studies that protoplasm is 

 a homogeneous structureless solution, probably an emulsion hydrosol, 

 i. e., a colloid in which both phases are liquid, one of them, the disper- 

 sion medium, being water. Normal cytoplasm is at all times non- 

 miscible in water, but readily degenerates into a condition in which it 

 is miscible. 



If, with these facts in mind, we consider the theories of morpholo- 

 gists as to the finer structure of the cell protoplasm based upon stud- 

 ies of cells fixed in various hardening agents, it becomes evident that 

 the possibility that the "foam structure" advocated by Biitschli, or 

 the "thread," "reticular," and "pseudo-alveolar" structures of Fro- 

 mann, Arnold, Reinke, and others, are all simply the effect of fixatives 

 upon colloid solutions, is very real. The objection always advanced 

 to these theories of protoplasmic structure, namely, that the structures 

 described were at least in part artificial productions, not present in the 

 normal living cell, and variously described and interpreted by differ- 

 ent investigators, because each worked with a chfferent hardening 

 fluid or different technic, is strongly supported by these observations 

 upon colloids. This matter will receive further consideration in the 

 next section. 



THE STRUCTURE OF THE CELL IN RELATION TO ITS CHEMISTRY 



AND PHYSICS" 



It is obviously impossible to separate nuclei, nucleoh, cytoplasm, 

 and cell membranes from each other (except with sperm heads) and 

 to isolate them in quantities sufficient for analysis, and therefore we 



=» Biol. Bull., 1918 (34), 307. 



'^ Reviews of the significance of cell structure for pathology are given by Benda 

 and Ernst in Zentrlbl. allg. Path., 1914, Bd. 25, Ergiinzungsheft. 



