DRUGS INFLUENCING BODILY HEAT 51 



3. Heat JRegulation. There are centres in the tuber cinereum, and 

 less important centres in the corpus striatum, which coordinate or adjust 

 the relations between the heat-producing centres and the centres for 

 heat-loss. The result is the uniform, normal temperature existing in 

 health whereby the production of heat, caused chiefly by muscular activ- 

 ity and favored by constriction of the superficial vessels, is balanced by 

 loss of heat — through flushing of the surface vessels, or sweating, and 

 by lessened muscular action and more rapid respiration. In the body the 

 fall of a few degrees of temperature causes shivering or violent muscular 

 action, together with marked constriction of the cutaneous vessels, which 

 leads both to greatly increased heat production and diminished heat loss. 



The heat-regulating centres may be compared to the thermostat set 

 to keep the temperature of rooms at a fixed point. This instrument acts 

 through the expansion and contraction of metal whereby the heat is 

 turned on or off. As in the thermostat, which preserves a uniform tem- 

 perature by regulating the heat-production and heat-loss, so in the body 

 the heat-regulating centres are set to keep the temperature at the normal 

 point for the species. As one may set the temperature in the thermostat 

 at any given point, within reasonable limits, so in the body the heat- 

 regulating centres may be set at a higher or lower level. In fevers 

 toxins set the heat-regulating centres at a higher point, while certain 

 drugs set these centres at a lower level. The highest temperatures fol- 

 low violent muscular action in the rigors of certain fevers. When the 

 heat-regulating centres regain control, and stimulate the centres for heat- 

 loss, sweating occurs and the fever rapidly falls (malaria). Fever is due 

 chiefly to increased heat-production, combined with a certain diminution 

 in heat-loss. 



Very recently it has been discovered that adrenalin secretion plays 

 an important role in the production of fever. Adrenalin seems to be 

 essential as an activator of the brain, enabling it to convert latent energy 

 into heat and motion. The brain, liver and adrenals form a kinetic system 

 for this end. To use a mechanical simile, the brain is the battery, 

 adrenalin is the oxidizer, the liver is the gasoline tank (glycogen), and 

 the muscles are the furnace in which combustion occurs. To go a step 

 further it appears that the thyroid gland is the pacemaker, since it regu- 

 lates the rate of discharge of energy. 



Is fever beneficial.? Artificial heating of animals to a temperature 

 of 104° F., after injection with fatal doses of bacteria, caused half to 

 survive while all the controls died. Again, the factitious production of a 

 chill in animals subjected to experimental infections, caused a subsequent 

 fever and cure of the infection. Fever is probably the result of toxins. 

 Whether these do or do not directly act on the heat-regulating centres 

 is unknown. 



Action. — Now as to the precise action of antipyretics. Some act by 

 diminishing metabolism, as quinine. Some dilate the superficial vessels 

 and may also cause sweating, as salicylic acid, alcohol, ammonium acetate, 

 nitrous ether, opium and ipecac. Some act by depressing the circulation, 

 as aconite, veratrum, digitalis, antimony and venesection. These lessen 

 metabolism. The modern, coal-tar antipyretics, as acetariilid, antipyrin 



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