ABNORMAL IRRITABILITY PRODUCED'BY SAuts 695 
irritability ; neither did sodium acetate nor other salts whose 
anions form soluble calcium compounds. 
But the sodium salts whose anions precipitate calcium 
promptly produce these reactions. NaF, Na,CO,, Na,HPO, 
sodium oxalate, sodium citrate,’ sodium tartrate give the 
contact reaction in a dilution of 1 gram-molecule in 8 or 10 
liters of water or even less. NaHCO, gives the reaction but 
requires a higher concentration, e. g., 1 gram-molecule in 4 
to 5 liters of water. If we put the muscle into a solution of 
Na,PO,, it goes at once into a powerful tetanus. This 
tetanus may be partly or wholly due to the high concentra- . 
tion of HO ions in this solution. When a muscle goes into 
tetanus in a solution, we cannot, as a rule, demonstrate the 
contact-reaction. Thus I have never succeeded in producing 
contact-reaction by a Na,PO, solution. NaH,PO, does 
not cause contact-irritability, but this is in harmony with 
our general result. 
The HO and H ions deserve special attention. In my 
experiments on rhythmical contractions I found that while 
they are not able to produce rhythmical contractions directly, 
they accelerate the beginning of these contractions in the 
presence of Naions. In addition to such a catalytic action 
common to both the HO and H ions, the former have another 
effect which they do not share with the H ions. The muscle 
produces constantly H,CO, and possibly other acids. These 
acids will increase the solubility of Ca salts and increase 
the number of Ca ions in the tissues. An addition of HO ions 
will counteract this effect. 
It is due to the presence of free HO ions that solutions 
of Na valerianate and Na formate give rise to a slight degree 
of contact irritability in muscle, although calcium formate 
and calcium valerianate are soluble. If we diminish the 
1The citrates require an alkaline reaction for the precipitation of calcium 
This condition is fulfilled in the fresh normal muscle. 
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