PERSPIRATION. 287 



In all the cases which have been mentioned, there is no reason 

 to suppose that exhalation did not continue, both on the skin and 

 in the lungs, so that the absorption must have been greater than 

 it at first sight appears. When no increase of weight has taken 

 place on immersion in the warm bath, absorption must have oc- 

 curred to maintain the weight, notwithstanding the cutaneous and 

 pulmonary losses ; and, when some decrease of weight has been 

 observed, we are not justified in concluding that absorption had 

 not taken place and not lessened the amount of the loss which 

 would have happened. Indeed, there is no doubt that per- 

 spiration is considerably increased in the warm bath. I may 

 remark that, while absorption is more active accordingly as more 

 fluid has been lost, it gradually becomes less as it approaches the 

 habitual standard of plenitude in the individual, and that, while 

 transpiration is increased by elevation, the proportion of absorp- 

 tion is increased by depression of temperature. z 



Dr. Massy, of America, about 1812, found that, if the body 

 were immersed in a decoction of madder, this substance became 

 discoverable in the urine by the alkalies ; and Dr. Rousseau, in 

 conjunction with Dr. S. B. Smith, made, in consequence, a num- 

 ber of experiments, from which they conclude that rhubarb and 

 madder are so absorbed, and that these only of all absorbed 

 substances can be discovered in the urine, and are seen in this 

 fluid only, and are absorbed by no other parts than the spaces 

 between the middle of the thigh and hip, and between the middle 

 of the arm and shoulder. a 



* 1. c. p. 98. sqq. 352. sqq. 



r * Discourses on the Elements of Therapeutics and Mat. Med. 1817. vol. i. 

 p. 56. sq. 



Vegetables perspire copiously during the day; not so much according to the 

 temperature, but to the intensity of light; and De Candolle found that lamps had a 

 similar power on the function to that of the solar ray, and proportionately to their 

 intensity. (Physiologie Vegetale, t. i. p. 1 12.) The number of pores or stomata 

 through which the fluid exhales, will also influence its quantity. Hales inferred 

 that a sunflower, three feet high, exhaled only twenty ounces, seventeen times 

 more, according to him, than would have been perspired from an equal extent of 



u 2 



