178 
moisture required for saturation, this will be raised in the 
lungs to something like 85 ° F., viz., a few degrees lower 
than the blood heat; at that temperature it can contain 
about ten times as much moisture as it could at 20° F., 
and will, therefore, carry off a large part of this amount 
from the lungs; or to put this another way, the amount 
of evaporation from the lungs will now be much the same 
physically as if we breathed air of 85° F. only containing 
about nine per cent relative moisture. This has already 
been pointed out by Brunner, Krieger, &c. ; and Mr. Steffen, 
the chemist here, published some tables, in which he re- 
duced the moisture in the air to the relative of the mean 
blood heat ( 37 ° Cel.), that is, he showed for each month 
what per cent of the quantity which air could contain 
at 37 ° C. was present in the atmosphere.* It seems to me 
that the principle thus dealt with is undoubtedly cor- 
rect, but I think that the figures require modification, 
because, as pointed out by Dr. Yolland, it is taken for 
granted that the air was raised to blood heat and expired 
saturated, neither of which are absolutely correct. I hope 
to enter more fully into this point when I have had the 
opportunity of collecting more data, and seeing what has 
been written on the subject. 
We must not forget that the physiological feeling of cold 
depends, to a large extent, upon evaporation, for perspiration 
is always taking place from the surface of the body, though 
we only notice it when it is abnormally great, and upon the 
rapidity with which this is removed hangs to a large extent 
our sensation of the air being dry or cold. We have already 
seen that the evaporation from the skin is, as a rule, great 
in Davos, and to this cause must, to a large extent, be 
attributed our sensation of the dryness of the atmo- 
sphere. 
* Die Meteorologisclie Verhaltnisse von Davos von W. Steffen. Basel, 
1878 * 
