CLOTHING AND THE ATMOSPHERE. 791 



would surprise the system while it is in the process of accommodation. 

 " The organization," says Dr. Pettenkofer, " is a prudent and faith- 

 ful servant, which will deliver itself and its master from trouble if 

 it is given time to set itself right and is protected against rude treat- 

 ment." The body, even when exposed stark naked to the air, is not 

 wholly without defense against heat and cold. It can, up to a certain 

 point, itself regulate the expenditure of caloric by the intervention of 

 the vaso-motor nerves that go to the capillaries of the skin. Cold pro- 

 vokes a shrinking of the little vessels, and, restraining the peripheric 

 circulation, diminishes the radiation and the transpiration to such a 

 degree as to protect the internal organs for a considerable time. Heat, 

 on the other hand, dilates the vessels so that the blood flows to the 

 surface and the caloric is in a certain way driven out. Unfortunately, 

 this automatic regulator, the play of which is commanded by the 

 nerves, is too easily disordered and its springs are too easily relaxed. 

 We can doubtless fortify it by exercise, harden ourselves, and habitu- 

 ate the body to support inclement conditions ; and there are peoples 

 and persons who have done wonders in this direction ; but the harden- 

 ing process works under limitations, and its results are not within 

 everybody's reach. The real regulators of the heat of the body are 

 clothes. 



The thinnest veil is a vestment in the sense that it moderates the 

 loss of heat which radiation causes the naked body to experience. In 

 the same way a cloudy sky protects the earth against too great cooling 

 in spring nights. In covering ourselves with multiple envelopes of 

 which we augment the protecting thickness according to the rigor of 

 the seasons, we retard the radiation from the body by causing it to 

 pass through a series of stages, or by providing relays. The linen, the 

 ordinary dress, and the cloak constitute for us so many artificial epider- 

 mises. The heat that leaves the skin goes to warm these superposed 

 envelopes ; it passes through them the more slowly in proportion as 

 they are poorer conductors ; reaching the surface, it escapes, but 

 without making us feel the chills which direct contact with the atmos- 

 phere occasions, for our clothes catch the cold for us. The hairs and 

 the feathers of animals perform the same function as toward their 

 skin, serving to remove the seat of calorific exchange away from the 

 body. The protection we owe to our clothes is made more effectual 

 by their always being wadded with a stratum of warm air. Each one 

 of us thus has his own atmosphere, which goes with him everywhere, 

 and is renewed without being cooled. The animal also finds under its 

 fur an additional protection in the bed of air that fills the spaces be- 

 tween the hairs ; and it is on account of the air they inclose that 

 porous substances, furs, and feathers keep warm. 



Experiments to determine the degree of facility with which differ- 

 ent substances used for clothing allow heat to escape were made by 

 Count Rumford, Senebier, Boeckmann, James Starck, and M. Coulier. 



