8 4 



DYNAMICS OF LIVING MATTER 



especially the sodium salts of these acids.* The experiment is as 



fyyi 



follows: If the gastrocnemius of a frog is put into a solution of 



o 



sodium citrate and left there for two or three minutes, it will go into 

 powerful tetanic contractions or rather cramplike clonic contractions 

 when taken out of the solution; while these contractions stop at once 

 when the muscle is put back immediately. This can be repeated at desire, 

 the muscle always going into contractions when exposed to the air, and 

 relaxing again when put back into the solution. Zoethout found that 

 this reaction can be produced quicker and with greater certainty when 

 a slight amount of a K-salt is added to the solution. I believe that the 

 K antagonizes the tendency to rhythmical contractions which the muscle 

 possesses in a sodium-citrate solution. It seems to be necessary that 



this tendency to rhythmical 

 contractions be overcome in 

 order to obtain the phenomenon 

 which we are now discussing, 

 and which I called in a pre- 

 liminary way the contact re- 

 action of muscle, inasmuch as 

 it can be produced by changing 

 the nature of the medium which 

 surrounds the muscle. The 

 apparatus used for the demon- 

 stration of this experiment is 

 shown in Fig. 15. 



When only part of the 

 muscle is lifted out of the 

 citrate solution, only those fibers 

 go into tonic contraction which 

 are in contact with the air; 

 while those fibers which remain 

 in the solution do not contract. 

 The reaction, therefore, is a 

 purely local one in each in- 

 dividual muscle cell. This re- 

 action not only occurs when 

 the muscle is brought from the 

 solution into contact with air, 

 but also when it is brought into contact with CO 2 , oil, toluol, sugar, 

 or glycerine solutions. All these solutions are nonconductors, and 



* Loeb, Am. Jour. Phy:iology, Vol. 5, p. 362, 1901. 



M 



D 



FIG. 15. 



