IN Mixep SoLurTions 399 
the case of zinc. Investigations by Swingle,* Clark,+ Rumm and 
others on the action of Bordeaux mixture, although concerning 
very different proportions from those here involved, all testify to 
this power of calcium to neutralize the poisonous action of copper. 
Whereas the presence of calcium reduced the harmful effects of the 
copper to about one fourth of that seen in the simple copper solu- 
tion, the antagonizing action of the calcium reduced the toxic ac- 
tion of the zinc to, at most, one sixteenth of that of the simple zinc 
solution. In the case of silver, the addition of calcium seemed to 
exert no ameliorating action. As far as the evidence at hand goes, 
it appears that such ameliorating action as was observed and would 
be expected stands in an inverse relation to the poisonous activity 
of the heavy metal. 
. From the above, as well as from the work of others, it appears 
conclusive that certain cations in mixed solutions exert a physio- 
logical action antagonistic to that exerted by other cations. The 
question next arises as to the nature of this modification and its 
seat. Does a mixed solution of calcium sulphate and copper sul- 
phate or copper chloride, for example, produce the change (which 
brings about this physiological result) by affecting the condition 
of the copper in the solution outside of the cell, or does it bring 
about modifications within the cell itself? Is this antagonism an 
extracellular chemical change or an intracellular physiological 
change ? 
We have two sorts of cases to deal with. In the one case the 
salts have a common anion and in the other case the anions differ. 
We may set aside any such changes as the formation of double 
salts or the setting back of molecular ionization in the former case, 
since it has been shown that like results are seen when the mixed 
salts have common anions. This would seem to be a probable situ- 
ation from a priori reasoning also, since in most cases the solutions 
of the salts of the heavy metals were so dilute that practically 
complete ionization took place. In that event, no matter what its 
associated anion was, the metal acted as free ions. 
* Swingle, W. T. Bordeaux Mixture. U. S. Dep. Agric. Div. Veg. Path. and 
Physiol. Bull No. 9. 1896. 
+Clark, J. F. The Toxic Properties of some Copper Compounds with special 
reference to Bordeaux Mixture. Bot. Gaz. 33: 26. 1902. 
