546 Medicine. [Chap. IV, 



illnstration by the use of heat, light, and food, after 

 coldness, darkness, and hunger, seems to fail in its 

 application to many morbid states of the system. 

 It a})pears, on the contrary, often to happen that 

 excitement and excitability are increased at the 

 5ame time, and perhaps still oftener that they are 

 diminished and wasted together*. The radical 

 defect in every inquiry of this kind is our unao 

 quaintance with the nature of the vital principle, 

 a defect which \\\(t scantiness and imperfection of 

 all human knowledge does not seem likely speedily 

 to supph^ 



In a review of the systematic arrangements of 

 medical knowledge which have been undertaken 

 in the course of the eighteenth century, it would 

 be improper to pass w^ithout notice the learned 

 and laborious work of M. Lieutaud, first physician 

 to the monarch of France, published nearly fifty 

 years ago, under the title of Synopsis Universce 

 Medicina, This singular work was attempted on 

 the plan of collecting all the facts that experience 

 has taught, without any reasoning concerning their 

 causes. But the total want of method, perhaps 

 the unavoidable result of the plan, continually in- 

 troduced such confusion as to render this perform- 



bability of his being muchj if at all, indebted to Dr. Brown. Dr. 



Hnrtley seems to have been the first who, clearly and with effect, 

 employed the principle of associutlori to account for the pheno- 

 mena of the animal economy. (See Observations on Man). It is 

 iVbt improbable that Dr. Darwin was indebted to him for some 

 hints in forming his great work. 



* The author is aware that Dr. Darwin's theory makes provi- 

 sion to meet tliis difficulty and to explain it > but v/hether tlie- 

 explanation be sufficiently satisfactory, remains to be decided. 



