REGULATION OF THE TEMPERATURE. 33 1 



100 C.) the pulse rises to over 160 per minute. The same is true in fever ( 70, 

 3, e). Liebermeister gives the following numbers in an adult : 



Pulse-beats, per min., 78'6 91 -2 99-8 108 '5 110 137*5 

 Temperature in C., 37 38 . 39 40 41 42 



(3) Increased Temperature increases the Number of Respirations. Under 

 ordinary circumstances, a much larger volume of air passes through the lungs 

 when it is warmed almost to the temperature of the body. Further, a certain 

 amount of watery vapour is given off with each expiration, which must be 

 evaporated, thus abstracting heat. 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, 

 whereby the increased respiration must act in producing an amount of heat greater 

 than normal ( 127, 8). This excess is more than compensated for by the cooling 

 factors above mentioned. Forced respiration produces cooling, even when the air 

 breathed is heated to 54 C, and saturated with watery vapour. 



(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 (whale) 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. 



(5) 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 39 C. to 37 C. 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. 



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 prevents it from giving 

 off too much heat. Summer clothes weigh 3 to 4 kilos., and winter ones 6 to 7 kilos. 

 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, sheep's wool, cotton wool, flax, 

 spun-silk, are given in order, from the worst to the best conductors. (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 as linen ; hence, the latter gives it off in evaporation more rapidly. Flannel 

 next the skin is not so easily moistened, nor does it so rapidly become cold by evaporation ; 

 hence it protects against the action of cold. (5) The permeability for air is of importance, but 

 does not stand in relation with the heat-conducting capacity. The following substances are 

 arranged in order from the most to the least permeable flannel, buck-skin, linen, silk, leather, 

 waxcloth. 



215. HEAT-BALANCE. As the temperature of the body is maintained 

 within narrow limits, the amount of heat taken in must balance the heat given off, 

 i.e. , exactly the same amount of potential energy must be transformed in a given 

 time into heat, as heat is given off from the body. An adult produces as much 

 heat in half an hour as will raise the temperature of his body 1 C. If no heat 

 were given off, the body would become very hot in a short time ; it would reach 

 the boiling point in thirty-six hours, supposing the production of heat continued 

 uninterruptedly. The following are the most important calculations on the 

 subject : 



