388 PROFESSOR C. R. MARSHALL ON THE 



better adapted for studying the inhibitory action of calcium. Some variability in the 

 reaction of the muscles of different frogs, and especially at certain times of the year, 

 is observed — the sartorii of many female frogs during February and March show no 

 movement whatever when placed in 0'6 per cent, sodium chloride solution — but in 

 my experiments a maximum of 0*02 per cent, of calcium chloride has been sufficient 

 to inhibit the contractions.* Often much less sufficed. In a normal salt solution 

 containing 0'2 per cent, of tetra-ethyl-ammonium chloride, a concentration of O'Oo 

 per cent, of calcium chloride was needed. In such a solution one or a few contractions 

 sometimes occurred when a fresh muscle was immersed, but these did not follow if the 

 muscle was transferred from a salt solution. 



Owing to the calcium present, the Biedermann contractions do not occur when a 

 muscle is placed in Ringer's solution. If, however, a sartorius is put into Ringer's 

 solution containing 0'2 per cent, of tetra-ethyl-ammonium chloride, periodic contrac- 

 tions of the whole muscle, usually but not invariably accompanied by fibrillary 

 tremors, follow. The contractions cause bending of the muscle outwards, the external 

 surface of the muscle forming the inner surface of the curve. All movements are 

 prevented by the addition of O'l per cent, of calcium chloride to the solution. After 

 the addition of 0"05 per cent, calcium chloride a few preliminary movements only occur. 

 The contractions are diminished but not annulled by the presence of 0"025 per cent, of 

 calcium chloride. When, however, sufficient calcium was present to prevent spon- 

 taneous movements, contractions could be induced for one to two seconds by probing 

 the muscle, especially about the point of entrance of the nerve. 



The factor of importance in this phenomenon of inhibition is apparently the actual 

 concentration of the calcium salt, and not its concentration in relation to the concen- 

 tration of the tetra-ethyl-ammonium chloride. To take an example, a sartorius muscle 

 in a solution isotonic with 0'6 per cent, sodium chloride, containing 1 in 3750 calcium 

 chloride, 1 in 1250 tetra-ethyl-ammonium chloride, and common salt, showed twitches 

 similar to but less frequent than those seen in the corresponding muscle of the opposite 

 side in a similar solution, but without calcium chloride. When the muscle was trans- 

 ferred to an isotonic solution containing double the amount of calcium chloride and 

 of tetra-ethyl-ammonium chloride, i.e. 1 in 1875 calcium chloride and 1 in 625 tetra- 

 ethyl-ammonium chloride, no spontaneous movements occurred. On being placed, 

 after surface drying, in the previous solution, movements again appeared and were 

 again inhibited when the muscle was placed in the stronger solution of calcium and 

 tetra-ethyl-ammonium chlorides. It would thus seem as if the inhibition were not 

 due to any association or combination of the tetra-ethyl-ammonium chloride with the 

 calcium chloride, and that this does not happen is also supported by the fact that 

 solutions of tetra-ethyl-ammonium chloride and of calcium chloride of the same 

 electrical conductivity show no change of conductivity when they are mixed. 



Action on Excised Frog's Muscle. — When an excised frog's muscle is immersed in 



* All the solutions used were made isotonic with 0"6 per cent, sodium chloride. 



