NERVOUS SYSTEM AND ANIMAL HEAT. 885 



the active habits of which, in high external temperatures, may furnish 

 sufficient oxidizable material in the metamorphosed blood and muscular 

 and nervous tissues, to maintain the temperature of their bodies ; but 

 Carnivorous animals consume also large quantities of fat, proportion- 

 ate, it may be remarked, to the coldness of the climate in which they 

 live. In warm climates, Man also might thus sustain his temperature ; 

 but in colder regions, where the loss of heat from the body is more 

 rapid, Man, like the Herbivora, whose habits are inactive, must rely 

 upon food also, as one source of oxidizable material ; and, like them, 

 upon food containing more carbon and hydrogen, and proportionally 

 less nitrogen. In diiferent persons, and in different seasons and cli- 

 mates, the extent to which carbonaceous and hydrogenous food is relied 

 on, as a source of combustible material, may vary. An elevation of 

 the external temperature will lessen the amount of oxidized food ; 

 whilst the opposite condition increases it. The excess of carbonic 

 acid exhaled in cold seasons, can only be accounted for by its pro- 

 ceeding from the greater quantity of food then consumed. On these 

 principles may be explained the fact, that no one dietary is economi- 

 cally adapted to all constitutions, occupations, habits, races, seasons, 

 or climates ; hence, the laborer requires a different diet to the seden- 

 tary student, and the native of the tropics different food to the Lap- 

 lander. 



Influence of the Nervous System in the production of Animal Heat. 



This was formerly greatly exaggerated, and was attributed to some 

 direct action of the so-called nervous force. Many researches upon 

 animals have shown that injuries to the brain, whether by sections, or 

 by the administration of narcotics, are- followed by a lowering of the 

 temperature of the body. (Brodie, Legallois, Wilson Philip, Hastings, 

 C. Williams, and Chossat.) 



In paralysis, from cerebral disease in Man, the paralyzed limbs are 

 usually of lower temperature than the sound limbs, the difference 

 sometimes being as much as 7. On the other hand, an elevation of 

 temperature in certain regions may follow local injuries of the nervous 

 system. Thus, when the spinal cord is divided in the middle of the 

 back, in a Warm-blooded animal, the lower half of the body may be- 

 come warmer, and remain o for some time. In complete 'paralysis of 

 the lower half of the body, in Man, from injury of the cord, a similar 

 increase of heat has been observed in the groin, viz.: 111. (Brodie.) 

 Besides these facts, there are many which show that general depress- 

 ing causes, acting on the nervous system, lower the temperature, 

 whilst excited conditions of that system are accompanied by increased 

 animal heat for example, exhaustion or fear on the one hand, and 

 strength or passion on the other. In the last instances the influence 

 of the nervous system is plainly indirect, and must be attributed to a 

 corresponding diminution or increase of the pulse and respiratory acts. 

 The ultimate influence of alcohol, in raising the temperature of the 

 body, may also be partly due to its specific stimulating effect on the 

 nervous system, and, through it, on the heart and respiratory organs; 



