ABNORMAL IRRITABILITY PRODUCED BY SALTS 705 



traction I may mention hard rubber, glass, filter paper, var- 

 nished and unvarnished wood, bone, muscle, all kinds of 

 metals. Among the liquids tried were oil, glycerin, sugar 

 solutions and several salt solutions. It is thus obvious that 

 in a sodium-citrate solution two influences are united, first 

 the effects of the citrate ion which causes a modification or 

 an increase in the irritability of the nerve, and second, the 

 liquid character of the solution. The latter is the direct 

 cause for the contraction. 



Another point is of interest in this connection. The 

 sodium-citrate or sodium-fluoride solution increases the elec- 

 trical irritability of the nerve so that it can easily be stimu- 

 lated by its own current of demarkation. This increase 

 occurs regularly before the twitchings of the muscle begin. 



In my experiments on artificial parthenogenesis in Chse- 

 topterus I found that there are two ways by which the 

 unfertilized egg can be caused to develop first, by certain 

 ions (K, H), and second, by causing the egg to lose water. 

 It follows froni the facts of dissociation that a loss of water 

 on the part of the egg must alter the proportion of ions in 

 the egg. It thus becomes possible that the artificial par- 

 thenogenesis produced by the loss of water is in reality an 

 ion effect. In regard to the twitchings caused by putting 

 the nerve into solution Mathews has shown that two cases 

 must be distinguished -first, the effect of specific ions, and 

 second, the effect of loss of water. Any solution whose 

 osmotic pressure is high enough can cause contractions if 

 the nerve be put into it. Is it not possible that the loss of 

 water in the nerve acts in the same way as the citrate or 

 fluoride ions? The limited solubility of CaSO 4 would make 

 this possible. I tried whether a nerve after having been 

 put into a 2n sugar solution long enough to cause muscular 

 contractions would show the above-mentioned mechanical or 

 contact-irritability. This was indeed the case. If such a 



