444 CLOTHING. 



body. Farther, a certain amount of watery vapour is given off with 

 each expiration, which must be evaporated, whereby heat is abstracted. 

 Energetic respiration aids the circulation, so that respiration acts 

 indirectly in the same way as (2). According to other observers, the 

 increased consumption of O favours the combustion in the body 

 (p. 259, 8), whereby the increased respiration must act in producing an 

 amount of heat greater than normal. This excess is more than com- 

 pensated by the cooling factors above-mentioned. Forced respiration 

 produces cooling, even when the air breathed is heated to 54C., and 

 saturated with watery vapour (Lombard). 



(4.) Covering of the body. Animals become clothed in winter with 

 a winter fur or covering, while in summer their covering is lighter, so 

 that the excretion of heat in surroundings of different temperatures is 

 thereby rendered more constant. Many animals which live in very 

 cold air or water are protected from too rapid excretion of heat by a 

 thick layer of fat under the skin. Man provides for a similar result by 

 adopting summer and winter clothing. 



The position of the body is also important ; pulling the parts of the 

 body together, approximation of the head and limbs, keep in the heat ; 

 spreading out the limbs, erection of the hairs, pluming the feathers, 

 allow more heat to be evolved. If a rabbit be kept exposed to the air 

 with its legs extended for three hours, the rectal temperature will fall 

 from 39C. to 37C. Man may influence his temperature by remaining 

 in a warm or a cold room by taking hot or cold drinks, hot or cold 

 baths remaining in air at rest or air in motion, e.g., by using a fan. 



Stimulation of the central end of a sensory nerve (sciatic) increases the surface 

 temperature and diminishes the internal temperature (Ostroumow, Mitropolsky). 



Clothing. 



Warm clothing is the equivalent of food. As clothes are intended to keep in the 

 heat of the body, and heat is produced by the combustion and oxidation of the 

 food, we may say, the body takes in heat directly in the food, while clothing pre- 

 vents it from giving off too much heat. Summer clothes weigh 3-4 kilo., and 

 winter ones, 6-7 kilo. 



In connection with clothes, the following considerations are of importance : 

 (1.) Their capacity for conduction. Those substances which conduct heat badly 

 keep us warmest. Hare-skin, down, beaver-skin, raw silk, taffeta, sheeps' wool, 

 cotton wool, flax, spun-silk, are given in order, from the worst to the best con- 

 ductors. (2.) The capacity for radiation, Coarse materials radiate more heat 

 than smooth, but colour has no effect. (3.) Relation to the sun's rays. Dark 

 materials absorb more heat than light-coloured ones, (4.) Their hygroscopic 

 properties are important, whether they can absorb much moisture from the skin 

 and gradually give it off by evaporation or the reverse. The same weight of wool 

 takes up twice as much water as linen; hence, the latter gives it off in evaporation 

 more rapidly. Flannel next the skin, therefore, is not so easily moistened, nor 

 does it so rapidly become cold by evaporation; hence, it protects against the 



