294 COLLOIDS IN BIOLOGY AND MEDICINE 



The difficultly mobile colloidal acid-protein ion immediately becomes 

 positively charged at the surface of a neutral medium, and should it 

 touch an acid medium its positive charge is raised and at the same 

 time the acid field becomes more negative as the following diagram 

 indicates : 



OH . CO NH 2 OH . CO NH 2 



OH - CO |< NH 2 + LH = OH CO h? NH 2 H + L 



OH- CO- -NH 2 OH- CO- - NH 2 



for the H ion moves faster than the L ion. Measurements of series 

 consisting of acids and acid albumin couples yielded potentials quite 

 large enough to account for action currents. 



The development of such diffusion potentials in muscle would not 

 be possible if the fibrils were not quite poor in salt and the sarcoplasm 

 quite rich in salt. Since both the fluid and the fibrillar portions 

 contain protein (see BOTTOZZI and his school) a couple consisting of 

 acid albumin/acid/acid albumin yields no current. The current is 

 reestablished through electrolytic dissociation of the acid albumin 

 due to the salt in the sarcoplasm (see p. 292). If such couples are 

 placed in series considerable electric tension (voltage) may be ob- 

 tained. 



These results are in agreement with the fact that the normal 

 properties of muscle are conditioned by definite states of swelling and 

 electrolyte content. 



If frogs' muscles are placed in an isotonic solution of cane sugar 

 or other nonelectrolyte (mannit, asparagin, etc.), they lose their 

 irritability (e.g., for the induced current) but retain their volume; 

 they do not swell as in distilled water in which the irritability is 

 likewise suspended. The ability to contract is restored by Na ions 

 (about 0.07 per cent NaCl) (C. E. OVEKTON) as well as by Li ions; 

 but it is not restored at all by K ions. The irritability is also sus- 

 pended by isotonic potassium and rubidium salts. If the anions 

 and cations are arranged in accordance to the extent with which 

 they interfere with irritability, we obtain lyotropic series similar to 

 those which we discovered for the salting out of colloids (see pp. 80 

 to 83); according to R. HOBER,* C. E. OVERTON* and SCHWARZ,* 

 they are as follows : 



inhibitory: K > Rb > Cs > Na, Li 



inhibitory: tartrate, SO 4 > acetate > Cl > Br,NO 3 > I > SCN. 



If an uninjured frog's muscle is dipped into an isotonic solution 

 of a neutral salt and the part so treated is united with another part of 



