ANIMAL HEAT. 



most effective methods of resisting the depressing influence 

 of cold is to constantly exercise the muscles ; and it is well 

 known, that after long exposure to intense cold, the tendency 

 to sleep, which becomes almost irresistible, if indulged in, is 

 followed by a very rapid loss of heat and almost certain 

 death. It is not necessary to cite the accounts of travellers 

 and others in support of these facts. In some animals, the 

 amount of increase in the temperature during muscular 

 activity is very great, and this is notably marked in the 

 class of insects. In the experiments of Newport, on bees 

 and other insects, a difference of about 27 was noted be- 

 tween the conditions of complete repose and great muscular 

 activity. 1 The same facts were observed by Dutrochet, but 

 he operated upon single insects, and observed an elevation 

 of only a fraction of a degree. 2 These facts are interesting, 

 as showing the very great elevation of temperature that can 

 be produced in the lower order of beings during violent ex- 

 citement ; but in man, the differences, though distinct, are 

 never very considerable, for the reason that violent mus- 

 cular exertion is generally attended with greatly-increased 

 action of the skin, which keeps the heat of the body within 

 very restricted limits. In the experiments of Newport, the 

 loss of heat from the surface was arrested by confining the 

 insects in small glass bottles. 



The effects of active exercise, as in fast walking or riding, 

 were very well observed by Dr. Davy. He found a con- 

 stant elevation in the general temperature (taken under the 

 tongue), amounting to between one and two degrees ; 3 but 

 the most marked effects were observed in the extremities, 

 especially when they were cold before taking the exercise. 4 



1 XEWPORT, On the Temperature of Insects, and its Connexion with the Func- 

 tions of Respiration and Circulation in this Class of Invertebrate Animals 

 Philosophical Transactions, London, 1837, p. 281. 



8 DUTROCHET, Recherches sur la chaleur propre des etres vivans d basse tempera- 

 ture Annales des sciences naturelles, Zoologie, Paris, 1840, 2me serie, tome xiii., 

 p. 43, et seq. 



3 DATY, Physiological Researches, London, 1863, p. 16. 4 Ibid., p. 11. 



