360 LECTURE XVI. 



a conception of the way the different elements are combined in the cell, 

 we need only to refer to the extremely delicate mechanism in the action 

 of the individual ions to make one realize how far we are from under- 

 standing fully the mechanism of the cell itself. 



Jacques Loeb by means of his comprehensive studies deserves great 

 credit for having added so much to our knowledge concerning the action 

 of salts and their reciprocal action, and especially by his work on arti- 

 ficial parthenogenesis. 1 At this place we can hardly take up in detail 

 these numerous and highly interesting investigations. We shall come 

 back to them again. A great number of such experiments have been made. 

 Unfertilized eggs of the Annelida may be developed by placing them 

 in sea-water to which a small amount of potassium salt has been added 

 (e.g., one or two cubic centimeters of 2J N.KC1 or KNO 3 solution to 100 

 cubic centimeters of salt water.) Such eggs develop apparently normal 

 larvae. Such a solution has no action upon the unfertilized eggs of the 

 sea-urchin. 



These experiments have been cited to show that the presence of inorganic 

 ions is indispensable for the life-process. The manner in which they 

 act is still unknown to us. It is possible that new light may be thrown 

 upon this question by a study of the other components of the cell, and 

 especially of their behavior towards the ions. Now the cells contain 

 colloids, and in fact the life process itself is intimately related to their 

 presence. There is no doubt that the peculiar physical condition of the 

 cell-contents is of great importance to all of the different processes which 

 take place within the cell. Indeed, this alone makes it possible for so 

 many different reactions to take place side by side. Colloidal solutions 

 diffuse but very slowly in fact, scarcely at all into one another. In- 

 creased viscosity of a medium, however, does not affect the rate of diffu- 

 sions of crystalloids and electrolytes, nor the mobility of the ions, nor does 

 it affect the degree of dissociation of electrolytes. A monomolecular reac- 

 tion (e.g., the catalysis of methyl acetate by dilute hydrochloric acid) 

 takes place in a jelly just as rapidly as in water. On the other hand, the 

 colloid, on account of its internal friction, often prevents the formation 

 of precipitates. This is effected, not by preventing the reaction from 

 taking place, but rather by keeping the newly formed molecules in such 

 an extremely minute state of subdivision that they do not come together 

 to form visible complexes. The colloids cause an enormous increase in 

 surface tension. 



The entire conception of colloids is in a stage of rapid development. 

 There is no way of defining precisely the part that they take in the life of 

 the cell. Many isolated facts indicate that the future investigation of 



1 Cf. Abderhalden: Arch. Rassen-und Gesellschaftsbiologie, Jg. I, p. 656 (1905). 



