682 GENERAL REVIEW OF THE NUTRITIVE PROCESSES. 



the following experiments recently performed by MM. Becquerel and Bres- 

 chet. The hair of Rabbits was shaved off, and a composition of glue, suet, 

 and resin, forming a coating through which air could not pass, was applied 

 over the whole surface. It might seem natural to suppose that, by preventing 

 the evaporation of the sweat, the temperature of the tissues would be very 

 sensibly increased ; and that, by this increase of the temperature of the whole 

 body, a high state of fever would be engendered, with the symptoms of which 

 the animal would at last die. But the contrary occurred. In the first Rabbit, 

 which had a temperature of 100 before being shaved and plastered, it had 

 fallen to 891 by the time the material spread over him was dry. An hour 

 after, the thermometer placed in the same parts (the muscles of the thigh and 

 chest) had descended to 76. In another Rabbit, prepared with more care, 

 by the time that the plaster was dry, the temperature of the body was not 

 more than 5| above that of the surrounding medium, which was at that time 

 69^; and in an hour after this, the animal died. These experiments place 

 in a very striking point of view the importance of the Cutaneous surface as a 

 respiratory organ, even in the higher animals : and they enable us to under- 

 stand how, when the secreting power of the Lungs is nearly destroyed by 

 disease, the heat of the body is kept up to its natural standard by the action 

 of the Skin. A valuable therapeutic indication, also, is derivable from the 

 knowledge which we thus gain, of the importance of the Cutaneous Respira- 

 tion; for it leads us to perceive the desirableness of keeping the skin moist, 

 in those febrile diseases in which there are great heat and dryness of the sur- 

 face, since secretion cannot properly take place through a dry membrane. Of 

 the relief afforded by cold or tepid sponging in such cases, experience has 

 given ample evidence. 



892. All the foregoing facts point to the formation of Carbonic Acid, by the 

 union of the Oxygen absorbed from the air with Carbon set free from the 

 body, as the main source of the evolution of Heat within the Animal sys- 

 tem. The precise mode in which this union is accomplished, is not yet 

 known; but it is certain that, in whatever manner the combination may take 

 place, a certain measure of caloric must be generated. The combustion of 

 from 5 to 10 oz. of Carbon per day, however, would be by no means suffi- 

 cient to keep up the temperature of the Human body to its proper standard ; 

 for it has been experimentally ascertained, that the amount of Caloric set free 

 by a warm-blooded animal in a given time is more than can be thus accounted 

 for. It does not hence follow, however, that we are to look to any other than 

 Chemical processes, for the explanation of this most important function; since 

 there can be no doubt that there are many other changes of composition, con- 

 tinually taking place in the living body, which have their share in the pro- 

 duction of the effect. These take place, for the most part, at the expense of 

 the surplus of Oxygen absorbed over that which is given out in the form of 

 Carbonic Acid; this surplus amounting to as much as 15 per cent, of the 

 whole ( 766). Of the manner in which this surplus is employed, no precise 

 account can be given; but there can be little doubt that part of it is expended 

 in uniting with Hydrogen, to form a portion of the watery vapour which is 

 exhaled from the lungs; and that another part unites with the Phosphorus 

 and Sulphur which are taken in as food (forming part of the proteine-com- 

 pounds ( 114), to be excreted as Phosphates and Sulphates ( 847). These 

 and other changes, in which the absorbed Oxygen participates, will be attended 

 with the evolution of Caloric; and thus we are probably to account for the 

 excess of Heat generated by a warm-blooded animal in a given time, above 

 that which would be produced by the combustion of the amount of Carbon 

 exhaled by it during the same period; as shown in the experiments of Dulong 



