ABNORMAL IRRITABILITY PRODUCED By SaLts 697 
It should finally be mentioned that sodium butyrate, 
sodium succinate and sodium asparaginate did not produce 
the contact-reaction. 
Having thus proved that sodium salts, whose anions 
precipitate calcium give rise to contact-irritability, it was to 
be expected that solutions of calcium salts would prevent or 
antagonize the contact-reaction. I found that by adding a 
small amount of CaCl, toa Na-citrate solution the latter solu- 
tion no longer produced the contact-reaction. The addition 
of lec. of a 5n CaCl, solution to 100 cc. of an effective 
sodium-citrate solution was sufficient to cause a muscle to 
lose its contact-irritability at once. Only after a prolonged 
stay in pure sodium-citrate solution does the contact-irrita- 
bility return. 
While all the facts thus seem to harmonize with the view 
that a decrease in the amount of Ca ions in the tissues (and 
possibly an increase in the amount of Na ions) is the essen- 
tial condition for the production of the contact-reaction, it is 
yet possible that the sodium salts whose anions form insoluble 
calcium compounds may have a specific effect upon other 
constituents of the protoplasm, e. g., proteids. 
III. ON THE NATURE OF THE APPARENT CONTACT-REACTION 
The reaction which we have provisionally called the con- 
tact-reaction appears when a muscle, after having been sub- 
merged in a sodium-citrate or any of the other above- 
mentioned effective solutions, is brought into contact with air. 
In this change from solution to air a number of conditions 
change and it is now our task to determine which is the 
essential one. 
As soon as the muscle is taken out of the solution and 
brought into air, more O, may diffuse into and more CO, may 
diffuse from the muscle. These two conditions have, how- 
ever, nothing to do with the reaction. The experiments 
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