40 RELATION OF THE TEMPERATURE OF THE AIR 
been reached in that direction yet. Above 70° F. of the air, the results 
are modified by the sweating that always accompanies so high a tem- 
perature if the body is clothed, and quite a different class of pheno- 
"mena appear, which have not been much studied. 
Page 130. 
In V and VII there was a slight fall of temperature at the moment 
of stripping ; this was probably connected with the perceptible moisture 
on the surface which evaporates almost immediately the clothes are 
removed. 
With regard to the nature of the clothing removed. It always had 
considerable non-conducting power, being composed in all cases of at 
least two layers of woollen material; though, as the observations in 
the warmer air were made in summer, and those in the colder, during 
corresponding seasons, the dress worn varied with the time of year, 
being thinner in the former and thicker in the latter. On the whole 
the amount of clothing worn does not seem to affect the results as 
long as there is sufficient to keep the body warm under ordinary cir- 
cumstances; and in the English climate to do this, one woollen cover- 
ing seems always essential. 
Some results obtained by Dr. V. Weyrich* with regard to the 
hygrometric condition of the skin at different temperatures of the 
atmosphere, obtained by means of an hygrometer specially adapted for 
the purpose, bear so fully on the subject under consideration that they 
will be here given. 
lst. When the body is clothed, the amount of moisture excreted 
by the skin does not vary appreciably when the observations are con- 
ducted in an air below 70°F 
2nd. When above 70° F. the amount of moisture excreted by the 
skin rapidly increases with a rise in the temperature of the atmo- 
sphere. 
It is thus seen that by means of an entirely different method of 
observation, Weyrich finds that in an air of: 70°F. sweating com- 
mences; and by a combination of his results with those arrived at 
from the facts given above, the following conclusions may be 
drawn :— 
With regard to the human body, when covered with badly con- 
ducting clothing, 70° F. is a critical temperature of the atmosphere. 
The removal of the clothing at that temperature produces sufticient 
contraction of the cutaneous muscular arteries to counteract the cool- 
ing effects of its loss, and consequently the internal temperature does 
not change; whilst on stripping at lower temperatures, the vascular 
contraction induced more than makes up for the covering lost, and is 
* “Die Unmerkliche Wasserverdunstung der Menschlichen Haut,” Leipzig, 
1862. Abstract in “ British and Foreign Medical Chirurgical Review,” Oct., 1863. 
