536 STUDIES IN GENERAL PHYSIOLOGY 



The concentration with which we have to deal in this case 

 is, according to him, 0.04 per cent, instead of 0.026 per cent, 

 of the serum. So far as the rhythmical contractions of the 

 muscle are concerned, the claim of Greene is incorrect. 

 When a muscle does not contract rhythmically in a NaCl 

 solution containing Ca, when the concentration of the CaCl 

 solution is 0.026 per cent., then no contractions occur at all 

 at a concentration of 0.04 per cent., or higher. For the 

 apex of the heart the relations are no different, and the claim 

 of Greene to the contrary rests, so far as I can see from his 

 paper, upon a misunderstanding. 



In observing the "stimulating" effect of the 0.04 per 

 cent. CaCl 2 solution the strip of heart muscle did not lie in 

 such solution, but hung in a moist chamber, and was moistened 

 with two or three drops of the CaCl 2 solution named. It 

 then began to beat rhythmically. If we assume that cal- 

 cium did indeed have something to do with this, we are still 

 not dealing in this case with the same condition of affairs 

 that we have when heart muscle is immersed in a large quan- 

 tity, about 100 to 200 c.c., of such solution. In the latter 

 case a larger number of Ca ions would enter the muscle in 

 the unit of time. By moistening the muscle with two or 

 three drops of a 0.7 per cent. NaCl solution containing 

 0.04 per cent. CaCl 2 the larger amount of the fluid runs off, 

 and the few Ca ions which enter the muscle are perhaps in 

 actual number equal to those which enter from a NaCl solu- 

 tion containing a very small amount, say 0.001 per cent. 

 CaCl g . Greene and Ho well have overlooked the fact that 

 the concentration of the solution is not the determining 

 factor in the latter case, but the number of molecules which 

 are driven into the muscle (through osmotic pressure). 

 When it is found that 100 c.c. of morphine of a certain 

 concentration kill a dog, and when it is further observed 

 that y-J-^ c.c. o e n morphine solution two or three times as 



