74 THE FLUIDS ACQUIRE A MOTION 



absorbent power of the skin for the liquid in contact 

 with it, a difference in the pressure below the sur- 

 face of the evaporating skin occurs. The external 

 pressure increases, and in an equal degree the pres- 

 sure from within towards the skin. If now the 

 structure of the cutaneous surface does not permit 

 a diminution of its volume, a compression (in con- 

 sequence of the loss of liquid by evaporation), it is 

 obvious that an equalization of this difference in 

 pressure can only take place from within outwards ; 

 first from within, and especially from those parts 

 which are in closest contact with the atmosphere, 

 and which offer the least resistance to the action of 

 the external pressure, 

 by which Hence it follows, that the fluids of the body, in 



the fluids 



acquire consequence of the cutaneous and pulmonary tran- 



a motion 



towards the spiration, acquire a motion towards the skin and 

 lungs. lungs, which must be accelerated by the circulation 



of the blood. 

 The change By this evaporation, the laws of the mixture of 



of pressure 



influences dissimilar liquids, separated by a membrane, must 



the mix- 

 ture of the be essentially modified. The passage of the food 



dissolved in the digestive canal, and of the lymph 

 into the blood-vessels, the expulsion of the nutritive 

 fluid out of the minuter blood-vessels, the uniform 

 distribution of these fluids in the body, the ab- 

 sorbent power of the membranes and skins, which, 

 under the actual pressure are permeable for the 

 liquids in contact with them, are under the in- 

 fluence of the difference in the atmospherical pres- 



