\'l DEDICATION. 



will perceive that the only method which can lead 

 to their final resolution, namely, the quantitative me- 

 thod, has been employed. 



The formulae and equations in the second part, 

 therefore, although they are not to be viewed as 

 ascertained truths, and as furnishing a complete, or 

 the only explanation of the vital processes there 

 treated of, are yet true in this sense : that being 

 deduced from facts by logical induction, they must 

 stand as long as no new facts shall be opposed to 

 them. 



When the chemist shews, for example, that the 

 elements of the bile, added to those of the urate 

 of ammonia, correspond exactly to those of blood, 

 he presents to us a fact which is independent of all 

 hypothesis. It remains for the physiologist to de- 

 termine, by experiment, whether the conclusions 

 drawn by the chemist from such a fact be accurate 

 or erroneous. And whether this question be an- 

 swered in the affirmative or in the negative, the fact 

 remains, and will some day find its true explana- 

 tion. 



I have now to perform the agreeable duty of 

 expressing my sense of the services rendered to me 

 in the preparation of the English edition by my 

 friend Dr. Gregory. The distinguished station he 

 occupies as a chemist ; the regular education which 



