PROTOPLASM 39 



Seifriz (1920) has investigated with care the viscosity of the proto- 

 plasms of a number of myxomycetes, algae, pollen tubes, protozoans, 

 and echinoderm eggs. He finds the degree of viscosity to vary widely, 

 from a very watery to a fairly rigid gel condition, not only in the different 

 organs of the cell but also in the protoplast as a whole at different stages 

 of its development. He warns against accepting viscosity alone as an 

 index of the gel or sol state of the protoplasm, since it is physical structure 

 and not viscosity which determines these states in an emulsion. 



It is to be hoped that the methods employed by the above investi- 

 gators will be further developed and applied more widely, for through 

 them many misconceptions will undoubtedly be corrected. 



It should be evident from all these considerations that there is prob- 

 ably no sinlge visible structure characteristic of protoplasm at all times. 

 Any fundamental structure which it may have remains to be discovered 

 in the ultramicroscopic constitution of the colloids and other materials 

 of which it is composed, and in the physical relations which these bear 

 to one another. It should be pointed out, however, that in the idea of 

 protoplasm as a complex colloidal emulsion we have the best hypothesis 

 yet offered as a basis for the interpretation of the behavior of living 

 substance. 



Chemical Nature of Protoplasm. Chemically, as well as physically, 

 protoplasm is exceedingly complex, and the study of its constitution has 

 opened a field of research which is continually broadening. Only a brief 

 summary of some of the more important chemical facts can be presented 

 here; for more detailed accounts special works on the subject must be 

 consulted. 1 



As already pointed out, the substances of which protoplasm is com- 

 posed are probably not fundamentally different from those found else- 

 where, but show rather a greater complexity and a high degree of 

 organization. Protoplasm is an intricately organized system of water, 

 proteins, enzymes, fatty substances, carbohydrates, salts, and other 

 minor constituents. The often cited analysis by Reinke and Rodewald 

 (1881) of the myxomycete JEihalium septicum (Fuligo) showed the proto- 

 plasm of this form to have the following composition : 



PER CENT DRY WEIGHT PER CENT DRY WEIGHT 



Proteins 40 Cholesterin (lipoid) 2.0 



Albumins and enzymes 15 Ca salts (except CaCO 3 ). . 0.5 



Other N compounds 2 Other salts .65 



Carbohydrates 12 Resins ... 1 .2 



p'ats 12 Undetermined 6.5 



The protein matter of protoplasm exists in relative complex forms. 

 "The chief mass of the protein substances of the cells does not consist of 



1 See especially the books of Hammarsten (1909), Wells (1914), Czapek (1915), 

 Bayliss (1915), Mathews (1916), Palladin (1918), Robertson (1920), and the review by 

 Zacharias (1909). 



