344 Hoyt: CULTURES OF SPIROGYRA 
It may be supposed that somewhat complex poisons emanating 
from the soil would be largely volatile (either as such or as their 
decomposition products, e. g., ammonia), and would thus be 
removed from the retort in the process of distillation. If such 
volatile material were still toxic and were retained in the receiver, 
the distillate would of course exhibit toxic properties. But the 
logical possibilities are here very numerous and a more detailed 
a priori consideration of this problem would be out of place without 
much more thorough experimentation than is now available. 
The toxicity of the waters here dealt with was probably due, 
in every case, to more than one substance; different portions of 
tap water varied in their injurious effects, different portions of 
ordinary distilled water were differently affected by redistillation 
in glass, and other lines of evidence might be deduced from the 
present studies to indicate that both waters contained more than 
one kind of injurious material. 
It appears highly probable that the beneficial effect on the 
ordinary distilled water of chalk, lime, agar, sphagnum moss, soil, 
and finely divided carbon, was due to their adsorptive action, a 
conclusion similar to that reached in the work of Nageli (20), 
Breazeale (5), Livingston et al. (11), and Livingston (12). In some 
cases all the poisonous substances seem to have been removed from 
solution, for the treated water was entirely nontoxic. The non- 
toxic water obtained by the distillation of tap water from animal 
charcoal contained more dissolved electrolytic material than did 
the toxic water prepared by simple distillation, as was shown by 
conductivity measurements kindly made upon these waters by 
Dr. W. Fraenkel, but the total salt content of the charcoal-treated 
water was calculated to be less than 0.01 per cent, so that the 
removal of toxicity seems not to be related to an increase in salt 
content. Furthermore, similar decrease in the toxicity of the 
water was brought about by substances which were chemically 
very unlike the charcoal used in these distillations. The small 
amount of chalk that failed to produce improvement when added 
to ordinary distilled water was much in excess of the amount 
dissolved, so that the marked beneficial effect of a larger amount 
of chalk cannot be considered as due to the addition of calcium to 
the water. The improvement produced by colloidal platinum and 
