193 



heavier than atmospheric air *." By wearing a 

 fleecy hosiery vest also next the skin for a month at 

 a time in the hottest parts of summer, he collected 

 an oily substance which accumulated on the nap : 

 this substance he exposed to a red heat in a silver 

 spoon, and, when burnt, it left behind a black pow- 

 der resembling in every thing the powder of char- 

 coal. " This all seems to prove," he adds, " that 

 phlogiston" (by which he can here mean nothing 

 else than carbon) " is emitted from the pores of the 

 skin f ." From the establishment of this power in 

 the skin, we obtain, besides, this additional and im- 

 portant fact, that carbonic acid may be formed out 

 of the oxygen gas of the atmosphere, when brought 

 into contact with the human body, without the neces- 

 sity or even the possibility of believing that the car- 

 bon entering into its composition, is derived from 

 the venal blood ; for the exhalent vessels of the skin 

 are all of arterial structure, and the fluids which 

 they contain and emit, exhibit nothing of the colour 

 or the properties of venal blood. 



153. The changes effected on the air by the eggs 

 of birds, may still farther elucidate this subject. 

 The shell of the egg is formed of carbonate of lime, 

 with a small portion of phosphate, united to an or- 

 ganic tissue. Spallanzani found it to be full of holes, 

 through which pass the extremities of very minute 

 vessels, coming off from the chorion, or membrane 

 with which the shell is internally lined : these vessels 

 terminate by small orifices on the surface of the 



On Insensible Perspiration, p. 82. f Ibid. p. 



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