140 Dr. Edwards, De V Influence 



I'impression qu'on re9oit est le rtjsultat de toutes ces actions com* 

 binees.'* 



" Lors meme que, par I'intensite de Tune d'elles, il nous arrive 

 de distinguer la cause qui nous affecte, I'observation de I'effet se 

 borne le plus souvent a la sensation, et les autres changemens qui 

 raccompagnent nous echappent. On conjoit par la que I'obser- 

 vation la plus attentive des pht^nomenes tels que la nature nous 

 les presente, ne saurait demeler dans cette combinaison d'actions 

 Teffet propre a chaque cause, ni reconnaitre des effets qui ne 

 seraient pas reveles par la sensation. 



" II est une m^thode qui regie les conditions exterieures, qui 

 fait varier celle dont on veut apprt^cier Paction, et qui fait juger, 

 par la correspondance entre ce changement et celui qui survient 

 dans I'economie, du rapport de cause et d'effet : c'est la methode 

 experimentale ; c'est celle que j'ai suivie. Pour en tirer parti il 

 fallait, d'une part, determiner I'intensite de la cause, d'autre part 

 celle de I'effet. La physique nous fournit ordinairement les 

 moyens de remplir la premiere indication." 



In the true spirit of philosophical investigation, Dr. 

 Edwards, in the first place, proceeds to examine the action 

 of physical agents upon the simplest forms, and least elabo- 

 rately developed organised beings, extending his inquiries 

 upwards, in the scale of the animal world, to man, the most 

 perfect creature, and the ultimate object of all physiological 

 researches. 



The peculiarity of constitution belonging to cold-blooded 

 reptiles, among which there is so little mutual dependance 

 of organs, renders these the best tests of the relative and 

 proportionate influence of the different agents^ the intense 

 action of which is liable to destroy the more perfect animals ; 

 and the great development of the nervous system in the 

 higher orders gives them a wider and more acute range of 

 sensibility. It is difficult, at all times, and often impossible, 

 to insulate corporeal functions among the warm-blooded 

 classes, so as to ascertain the amount and limits of physical 

 agency. The four classes of vertebrated animals, or such as 

 are furnished with true spines, afford ample means of com- 

 parative illustrations; and these departments hav engaged 

 the author's attention, in order to display the result of the 

 action of the same agent exercising a uniform influence upon 

 constitutions very differently constructed. The air, for 

 example, exercises its influence uniformly upon he four 

 mentioned classes of vertebrate, and their different families 

 are similarly exposed to the action of the atmosphere by 

 respiration. 



Curious and interesting as is this eubject, it is singular 



