ABNORMAL IRRITABILITY PRODUCED BY SALTS 693 



H 



shortening. But as soon as it is taken out of the solution 

 and comes in contact with air, it goes into tetanus or per- 

 forms a series of powerful contractions. The tetanus or the 

 contractions cease at once and relaxation of the muscle 

 occurs when the muscle is put back into the solution. 



It was found that not only the change of contact from 

 the above-mentioned solutions to air but 

 also to a number of other media produce 

 these contractions. What the nature of 

 the stimulus in this case is I cannot say 

 definitely. Provisionally I will assume 

 that we are dealing with contact-irrita- 

 bility and I will call the above-mentioned 

 reaction of the muscle the contact-reac- 

 tion. It would seem as though the en- 

 trance of the anions of the above-men- 

 tioned solutions caused a change in the 

 superficial layer of the muscle or its 

 individual fibers, either by precipitating 

 calcium or by otherwise altering the con- 

 stitution of the protoplasm. This change 

 is intensified by the increase in Na ions 

 in the same layer. In this condition the muscle is sensitive 

 to the nature of the substance with which it comes in contact. 



In these experiments one end of the gastrocnemius of a 

 frog is tied to a glass rod, G (Fig. 162), and the other end 

 is tied to the lever, L. A dish, D, containing the solution 

 is raised from below when we wish to submerge the muscle, 

 and is lowered when we wish to bring the muscle into con- 

 tact with air. 



In order to demonstrate the contact-irritability I used a 

 solution of 1 gram-molecule of sodium fluoride or sodium 

 citrate, etc., in about 8 or 10 liters. If the fresh gastrocne- 

 mius of a frog be put into such a solution for about one 



FIG. 162 



