PROTEINS AND PROTOPLASMIC STRUCTURE 



Laxjrence S. Mover 

 Department of Botany, University of Minnesota 



It is obvious that some kinds of protoplasm, such as the chromo- 

 somes, have an intricate structure, but in the case of morphologically 

 undifferentiated cytoplasm it is not self-evident that structure is 

 present. It will be the purpose of this chapter to correlate recent 

 results in this field with what is known about proteins. No attempt 

 will be made here to discuss specialized structures such as the cell 

 membrane. 



The physiological behavior of protoplasm indicates the presence 

 of some sort of structural continuity. Led by a desire to interpret 

 its properties in terms of structure, numerous investigators have 

 turned to the microscope for aid, yet have achieved little success. 

 For, under the microscope, protoplasm appears, to use the words of 

 von Mohl (27) , as "niemals einen klaren wasserigen Zellsaft . . . 

 sondern . . . eine zahfliissige, mit feinen Kornchen gemengte, 

 ungefarbte Masse." His description, it will be noticed, stresses its 

 gelatinous consistency. Later observers of living protoplasm have 

 emphasized the presence of emulsion droplets and granules but 

 have really left the subject of protoplasmic structure as obscure as 

 before; for it is hard to imagine how a disperse phase can furnish 

 the continuity needed to transmit stimuli. In any case, it has been 

 found that optically clear protoplasm can remain alive. Thus, an 

 amoeba may extend a pseudopodium free from granules. This can 

 be cut off with a microdissection needle yet retains its irritability 

 for a time (7) . Harvey (15) centrifuged sea urchin eggs into two or 

 more parts, one with the nucleus and the fat droplets, the other with 

 the pigment granules, yet each could be activated by chemical treat- 

 ment resulting in parthenogenetic cleavage. Thus it appears that 

 neither the nucleus nor the granules is needed to bring about cell 

 division. Hence it is generally realized that the hyaline, continuous 

 phase hides the answer to the problem. 



The mere fact that the hyaloplasm is optically empty does not 

 signify that it is structureless. For instance, the nuclei in the pan- 

 creas of the white mouse cannot be seen in the living cells although 



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