Ion-PROTEID COMPOUNDS 547 
or K solutions to the NaCl solution, it will no longer cause 
rhythmical contractions in a fresh muscle. It therefore 
looks as if the substitution of certain quantities of Na ions 
for Ca ions caused contractions; but if this substitution goes 
too far, the muscle loses its irritability. On the other 
hand, the presence of Ca ions in the NaCl solution prevents 
the substitution of a sufficient number of Na ions for Ca 
ions, and in the muscle thus prevents rhythmical contrac- 
tions. It is due to the presence of Ca (and K) ions in our 
blood that our muscles do not contract rhythmically. 
These facts received further support when I tried to 
determine the active alkalinity of the blood. I had found 
that a slight decrease in the active alkalinity of sea-water 
retarded the development and growth of young sea-urchins, 
while a slight increase in the number of hydroxyl ions 
accelerated both processes. It seemed to me that the main 
physiological interest in the alkalinity lay in the osmotic 
pressure of the free HO ions in the blood or serum, as 
only the free HO ions can have any physiological effects. 
In the course of my experiments I found that the quantity 
of free HO ions in the blood is neither increased by a 
considerable addition of NaHO nor decreased by a con- 
siderable addition of HCl.’ Experiments proved that this 
is not due to the salts of the blood or serum, but to the 
proteids. It is evident that the latter have the power of 
combining with H and HO ions. Spiro came to a similar 
result by starting from a different point of view.? Here 
again we have to deal with ion proteids. 
If we look at this phenomena from a biotechnical view- 
1 SPIRO AND PEMSEL, Zeitschrift fiir physiologische Chemie, Vol. XXVI (1898), 
p. 233, 
2 The experiments consisted in this, that I added various quantities of acid or 
alkali to ox blood and examined how long the muscle of a frog remained alive in 
such a solution. While the addition of a small amount of acid or alkali to a 
physiological salt solution renders the latter toxic for the muscle, a very much larger 
quantity of acid or alkali is required to make the blood toxic for the muscle. 
[1903] 
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