30& Dr. Edwards, De V Influence 



De rinjluence des Agens Physiques sur la Vie, Par 

 W.F.Edwards, D.M., &c. 



[Continued and Concluded.] 



Our analysis of Dr. Edwards's treatise terminated in the last 

 number but one with the influence of respiration over the 

 production of heat in vertebrated animals. The remaining 

 chapters are devoted to experiments illustrating the pheno- 

 mena of transpiration, absorption, temperature^ light, &c., 

 with applications to the human system. 



It is impossible to allude to transpiration without immedi- 

 ately conjuring up in imagination the figure of old Sancto- 

 rius and his balance, the honest physician accurately weigh- 

 ing himself, so as to calculate his losses by transpiration at 

 different periods, and compared with the quantities of food 

 which he swallowed. But, in his days, the knowledge of 

 physics was at a very low ebb, and hence his aphorisms re- 

 quire the more finished touch of modern physiology. 



It appears, that in twenty-four hours the losses which the 

 body sustains in weight are not equal throughout the day 

 and night, but exhibit fluctuations, depending on various 

 circumstances referrible to ph3^sical and vital causes. Among 

 the first may be reckoned temperature and pressure, dryness 

 and humidity, repose or agitation of the air ; and among the 

 second are, the constitutional health, repose and activity of 

 the body, &c., while some of the physical causes possess a 

 double influence, both vital and physical, such as light. 

 Under such circumstances it is clear, that knowledge of phy- 

 sical laws is essential, in order to compute the individual in- 

 fluence of physical agents in retarding or accelerating tran- 

 spiration. The importance also of this function in the animal 

 economy enhances the value of an intimate acquaintance with 

 its vital relations. 



The influence of food upon transpiration is the first object 

 of inquiry. Sanctorius declares this function to be feeblest 

 during the first three hours after a meal. But Dr. Edwards 

 agrees with others in denying the direct tendency of stomachal 

 digestion to retard transpiration. The presence of food in 

 the digestive canal attracts thither, it is true, a flow of liquids 

 from the surface of the body, and thus creates a temporary 

 diminution of transpiration. 



Sleep seems to possess a direct influence over transpiration 

 in increasing its quantity, as is seen in children at different 

 ^ges, whose bodies are bedewed with fluid under circum-. 



