352 SCIENCE PROGRESS 



an appearance, of course, indicating a heterogeneous structure 

 for the fixed plasma. 



The living material of the plant cell in many cases thus 

 exhibits a structure which we have been led to attribute to that 

 type of colloid solution, the hydrosol. This was perhaps the 

 most important fact established by Gaidukov's researches. As 

 has been mentioned above, with the gradual development of 

 the study of the physics and chemistry of colloids it became 

 increasingly evident that the protoplasm was to be regarded as 

 a complex of this type. Thus the activity of the cell depends in 

 a certain measure on the activity of the colloid hydrosol, and 

 the death of the cell and coagulation of the colloid complex are 

 probably closely inter-related ; in fact, we may say that the 

 coagulation of the hydrosol causes the cessation of living pro- 

 cesses in the protoplasm, and the irreversible change hydrosol 

 — hydrogel, is synonymous with death. This, at least, appears 

 to be Gaidukov's view. 



There are, however, those cases of cells which do not appear 

 to show the hydrosol structure, to be considered ; for here also, 

 in most cases, the protoplasm must certainly be regarded as in 

 an actively living state. It may be said that most cells which 

 permitted of favourable observation did show Brownian move- 

 ment, and Gaidukov considers that the cases referred to may 

 possibly be explained as follows : the particles in a young cell 

 are much more difficult to make out, and the Brownian move- 

 ment is more difficult to observe, chiefly, it would seem, through 

 the close proximity of the particles of the disperse phase in 

 the continuous phase. The same reasoning, he thinks, may 

 apply to these other cells, the particles being too close and 

 too small to manifest their motion by this method. What- 

 ever the explanation may be, however, there is no doubt 

 that the protoplasm is not to be regarded as a single type 

 of complex, but a series of different colloids with differing 

 properties in different cases — " the protoplasm is very poly- 

 morphic." 1 



A short summary of the main conclusions reached by 

 Gaidukov may be useful, although involving some repetition of 

 what has already been described. 2 



1 Gaidukov, I.e. p. 61. 



2 Gaidukov, v. Bechold, Die Koll. in Biol, und Med., p. 256. (Steinkopff, 

 Dresden, 1912.) 



