June 19, 1903.] 



SCIENCE. 



981, 



produced in the protoplasm by these means. 



The results of the experiments seem to show 

 that in these forms, also, the colloidal par- 

 ticles in the protoplasm carry a definite elec- 

 trical charge, and to demonstrate further that 

 the sign of the charge depends directly on 

 certain external conditions surrounding the 

 organism. 



The results of a series of experiments car- 

 ried on last year on the effect of variations 

 in temperature on unicellular animals sug- 

 gested a very close similarity between the 

 reaction of these organisms to variations in 

 the temperature, and the effects of the same 

 temperature variations on artificial colloidal 

 solutions as observed by Hardy and others. 

 This fact, and especially the conclusions of 

 Dr. Mathews on the chemical stimulation of 

 the nerve, led me to test the effects on the 

 protoplasm of Paramoscia, and other protozoa 

 of a series of solutions of acids, bases and 

 salts, with the following results : All the acids 

 and the solutions of all the salts with a pre- 

 dominant positive charge that were used in 

 the experiments, had a common effect on the 

 Paramcecia, viz., a coagulation of the proto- 

 plasm, and the formation of simple resting 

 cells, similar to those formed by low tempera- 

 tures. Likewise all bases, and the solutions of 

 all salts with a predominant negative charge, 

 had one and the same effect, viz., a liquefac- 

 tion of the protoplasm and a stimulation of 

 the metabolic activity of the organism, similar 

 to the effects of a slight increase in tempera- 

 ture. The following solutions carrying a pre- 

 dominant positive charge were used: m/800 

 HCl, H,SO, and HNO,; m/160, mg Ch, CaCl,, 

 Bad, and Ca(]Sr03).; and the following with 

 a predominant negative charge, m/800 

 NaOH, KOH and Ba(OH),; m/160 Na.SO,, 

 (NHJ^C.O,, Na^HPO, and Na^C.H.O,. The 

 rapidity and extent of the coagulation or 

 liq\iefaction vary directly with the valence 

 of the salt. Thus the phosphate and citrate 

 are effective in greater dilutions than the 

 sulphate. The exact figures will be given in 

 the complete paper. 



The Paramoscia used in the above experi- 

 ments were taken from cultures which were 



slightly alkaline in reaction. It was found 

 that if just enough hydrochloric acid was 

 added to the culture to give it a trace of free 

 acid, the reaction of the Paramoscia to the 

 salt solutions was nearly reversed. The pro- 

 toplasm of Paramoscia from such an acid cul- 

 ture is either not affected by the solutions of 

 salts with a predominant positive charge, or 

 in some cases is slightly liquefied. But such 

 an acid-modified protoplasm is coagulated in 

 most instances by the solutions of salts with 

 a predominant negative charge. These re- 

 sults agree almost exactly with Hardy's on 

 the acid and alkaline modified colloidal solu- 

 tions of egg albumen, and lead to the con- 

 clusion that in the living protoplasm of Para- 

 mmcium, as well as in artificial colloidal solu- 

 tions, the charge which the colloidal particles 

 carry depends directly on the reaction of the 

 surrounding medium. 



The chemotaxis of Paramcecia from alkaline 

 and acid cultures was tested, and it was found 

 that this response, also, may be reversed by 

 changing the reaction of the culture. For 

 example, Paramcecia from an alkaline culture 

 are negative, while Para^mcecia from an acid 

 culture are positive to weak hydrochloric acid. 

 It thus seems probable that the sense of the 

 chemotropic response of Paramcecium depends 

 upon the sign of the charge carried by the 

 protoplasmic particles. 



If it is true that the charge on the colloidal 

 particles in the protoplasm of Paramoecium 

 may be reversed by changing the reaction of 

 the surrounding medium, then Paramcecia in 

 an acid solution ought to show a different re- 

 sponse to the electric current from Paramcecia 

 in an alkaline solution, and experiments 

 showed this to be the case. Paramcecia in an 

 allsaline culture are strongly negative to the 

 electric current. If, however, a few cubic 

 centimeters of the culture containing the 

 Paramcecia be isolated in a small dish, and 

 weak hydrochloric acid added, drop by drop, 

 a point is soon reached at which some of the 

 Paramcecia begin to swim toward the anode 

 and this reaction may be increased by a 

 further addition of acid until half of the 

 Paramcecia show a decided positive response. 



