STRUCTURE OF CELLS 43 



agents, such as osinic acid, formalin, and liidiloride of mercury, pro- 

 duces just the same differences in the structure of colloidal solutions 

 that they i)roduce in the protoplasm of cells hardened by them. 

 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. g., 

 glycogen) or they may swell up [e. <j., nnu'in graiuiles), thus giving 

 the appearance 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 anj'thing 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. 



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 Riitschli, 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 struc- 

 tures described were artificial productions, not present in the normal 

 living cell, and variously described and interpreted by differ- 

 ent investigators, because each worked with a different hardening 

 fluid or different technic, is strongly supported by these observations 

 upon colloids. The possibility that the living protoplasm is homo- 

 geneous still remains open. This matter will receive further consid- 

 eration in the next section. 



THE STRUCTURE OF THE CELL IN RELATION TO ITS CHEMIS- 

 TRY AND PHYSICS -^ 



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

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

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

 are still quite uncertain as to just the chemical differences that exist 

 between them. That there are differences is certain, and by means of 

 micro-chemical reactions, by comparing analyses of cells in which nu- 

 e'eus or cytoplasm predominate, and by stud^ying their physico-chem- 

 ical relations to one another, we have arrived at more or less tangible 

 ideas on the question of the relation of the structural elements of the 

 cell to its composition. 



23a Reviews of tlio siffnificanoo of cell struetiirp for patholofry arc pixcii by 

 Benda and Ernst in Zentrlbl. allp:. Path., 1014. P>d. 20. Erfriinzunpslipft. 



