152 Dr. Edwards, De VInflumce 



in water and in air, frogs were found to gain an addition to 

 their weiglit according to the term of their continuance in 

 the former medium. An absorption of water was rendered 

 evident by the loss of bulk it had sustained, when measured 

 after the experiment. 



Thus, when the comparative influence of water and air is 

 estimated, the former appears to be absorbed, and adds to 

 the weight of the body ; and the latter tends to diminish the 

 weight, by different and fluctuating degrees of evaporation 

 taking place, and dependent much more on the degree of 

 motion in the air, than on its dryness or humidity : these last 

 conditions modify evaporation in a minor degree, when com- 

 pared with the influence of a current of air. 



The celerity of abswption exceeds that of transpiration six 

 times, in the most rapid cases. It therefore results, that the 

 losses by transpiration in air should be repaid by absorption 

 of water in a much less time than the expenditure occurs. 

 But the decrease of weight is not prolonged ; it is sudden, 

 and not continuous, alternating with augmentation of weight, 

 by absorption of liquid going on in a ratio superior to the 

 loss ; and thus nature's provision is manifested for the nutri- 

 ment of the body. 



With this last inquiry Dr. Edwards concludes the first 

 part of his work ; and it is observed, that, with regard to 

 transpiration, the losses of weight have been considered with- 

 out reference to the existence of any other influence than 

 water. The losses by transpiration have been examined 

 generally without regard to the matters lost. What relates 

 to water difi*ers essentially in one respect from that which 

 regards the air. The losses sustained by the body ought to 

 be more particularly examined. Temperature and loss of 

 time require estimation. An excretion of solid matter evi- 

 dently takes place ; for the water, in which animals are 

 submersed, becomes turbid, especially in hot weather, and it 

 sensibly contains animal matters, afiecting the weight of the 

 body in water. 



When animals are submersed in water, their skins exercise 

 two functions, acting inversely in determining their weight. 

 And it results, from comparative experiments, that the 

 absorptio7i at zero exceeds the loss in water ; while at thirty 

 degrees the loss exceeds the increase by weight from absorp- 

 tion ; and the higher the temperature, the greater is the 

 excess in the discharge of animal matters. We may therefore 

 presume, that the agency of temperature produces analogous 

 effects, upon aerial transpiration, to those before observed 



