STRUCTURE OF PROTOPLASM OF PARAMCECIUM. J 



gists until, very recently, attention was directed to them by the 

 work of Loeb, 1 Mathews, 2 R. S. Lillie and others. Mathews, 

 in particular, in his work upon the chemical stimulation of the 

 motor nerve of the frog, has arrived at the conclusion that the 

 protoplasm of the nerve is a colloidal solution whose particles 

 carry a definite electrical charge, and that stimulation of the 

 nerve is accomplished by a reversible change in the physical state 

 of the protoplasm, analogous to coagulation. He finds that this 

 stimulation or coagulation is effected chemically only by a series 

 of electrolytes which agree in carrying a predominant negative 

 charge of electricity, as would be the case 'in Hardy's positively 

 charged colloidal solutions. It is only fair to say that these 

 remarkable investigations of Mathews have been the inspiration 

 of this work on the physical structure of protoplasm. R. S. 

 Lillie 3 shows, in his work on the reaction of cytoplasmic and 

 nuclear structures to the electric current, that these forms of pro- 

 toplasm behave exactly as would positively and negatively 

 charged colloidal solutions under the same conditions. 



The experiments described above have shown that proto- 

 plasm reacts to various external conditions in a manner strictly 

 parallel to the behavior of colloidal solutions in the presence of 

 like stimuli. But meanwhile we have had but little evidence of 

 the precise structural changes, that accompany these reactions, 

 and are, as we have seen, the leading distinguishing feature of 

 colloidal solutions. It was with the idea of studying these struc- 

 tural changes, which occur in protoplasm when subjected to vari- 

 ous external stimuli, and of comparing them with the changes in 

 colloidal solutions under the same conditions, that the following 

 experiments were undertaken. . 



The material used has been the protoplasm of various proto- 

 zoa, viz : Paramcecium, Stcntor, Amccba and others, which are 

 ideal objects for this study because of the abundance in which 



1 Loeb, as a result of his work on the stimulation of contractile tissue by ions, and 

 on the toxic and antitoxic effect of ions on the duration of life of the Fundulus egg 

 and frog's muscle, was the first to suggest, that the protoplasm reacts under these 

 conditions like artificial colloids, although he has elsewhere adopted a different 

 explanation. (See Amer. Jour. Physio!., 1902, VI., p. 411.) 



2 Mathews, Science, 1902, XV., p. 492; 1903, XVII., p. 729. 



3 Lillie, Amer. Jour. Physio!., 1903, VIII., p. 273. 



