RHYTHMICAL CONTRACTIONS IN MUSCLE 537 



strong does not injure the dog, the conclusion cannot be 

 drawn from this that a morphine solution is more harmless 

 the greater its concentration, I do not doubt but that, 

 when a ventricle which does not beat in a 0.7 per cent. NaCl 

 solution containing 0.026 per cent. CaCl 2 is introduced in- 

 to a 0.7 per cent, solution containing 0.04 per cent. CaCl 2 , 

 and the quantity of the solution is the same in both cases, 

 the ventricle will not beat in the latter case either. Whether 

 a very dilute CaCl 2 solution, the concentration of which lies 

 far below that of the serum (that is, far below 0.026 per cent.), 

 is able to augment the stimulating effect of a NaCl solution 

 is yet to be tested, and might easily be made to harmonize 

 with what has been said above. 



14. Conclusions. 



a) There are certain ions for example, Na, Cl, Li, F, 

 Br, I, and others which (in solutions having an osmotic 

 pressure of 4.91 atmospheres) are capable of calling forth , 

 rhythmical contractions in muscles. These contractions are 

 not brought about in that the given ions increase the irrita- 

 bility, since, first, these contractions may continue even when 

 the irritability has been diminished; and, secondly, since in 

 solutions of non-electrolytes (for example, glycerin and 

 sugar) of the same osmotic pressure these contractions do 

 iwf occur even when the tissues have their normal irritability. 

 It is to be believed rather that the entrance of the ions 

 mentioned above into definite compounds in the muscle is 

 the cause of these contractions. 



6) There are ions which inhibit the liberation of rhyth- 

 mical contractions of the normal muscle; for example, Ca, K, 

 Mg, Be, Sr, Co, and Mn. The inhibiting effect of Ca, K, 

 and possibly also the other ions, does not rest upon the fact 

 that they reduce the irritability of the muscle; for through 

 the addition of only a small amount of CaCl 2 to a physi- 

 ological salt solution the contractions are prevented, while 



