694 STUDIES IN GENERAL PHYSIOLOGY 



minute, the muscle will show a slight contraction when 

 taken out of the solution. If the process be repeated, a 

 stronger contraction will follow when the muscle is removed, 

 and after a series of submersions have occurred the muscle 

 will give one or a series of powerful contractions every time 

 it is taken out of the solution and brought into contact with 

 air. After a certain time, which may be an hour or more, 

 and which varies according to the solution, the reaction 

 becomes weaker and finally ceases. 



If we use a stronger concentration than 1 gram-molecule 

 in 8 liters, we get more powerful contractions, but the irri- 

 tability of the muscle disappears sooner. 



II. THE NATURE OF THE SOLUTIONS WHICH PRODUCE CONTACT- 

 IRRITABILITY IN MUSCLE 



Solutions of cane-sugar or urea were unable to produce 

 the contact-reaction in muscle. I have tried these solutions 

 in all concentrations from to normal or even 2n. A large 

 number of electrolytes were then tested. None of the salts 

 of Li, K, Ca, Mg, and NH 4 gave rise to the contact-reaction. 

 This statement is based upon experiments with LiCl, Li 2 SO 4 , 

 Li 2 C0 3 , KC1, K citrate, K oxalate, MgCl 3 , MgSO 4 , NH 4 C1, 

 (NH 4 ) 2 CO 3 , and ammonium citrate. The degree of dilu- 

 tion used was as a rule 1 gram-molecule in about 8 or 10 

 liters. In some instances stronger solutions were tried, but 

 with the same negative result. 1 



In my experiments on rhythmical contractions I have 

 shown that the sodium ions have a specific role in the pro- 

 duction of these contractions. It seemed also possible that 

 they play such a role in the production of the contact-irrita- 

 bility. But I found that f or even stronger solutions of 

 NaCl, NaBr, Nal, NaNO 3 did not bring about the contact- 



i Zoethout showed later in my laboratory that the addition of a trace of potas- 

 sium citrate to the sodium-citrate solution facilitates the production of contact- 

 irritability. [1903] 



