METHODOLOGICAL INTRODUCTION. 15 



from nothing ! It was this method alone which exposed the perfect 

 nullity of the obstinately defended dogma of the c vital force.' 



Statistico-chemical investigations may serve as checks to, or 

 confirmations of other enquiries and methods of enquiry ; thus, 

 for instance, Boussingault, by a comparison of the amount of 

 nitrogen in the excrements with that in the food, has fully con- 

 firmed the experiments made by Dulong, Valentin, Marchand, and 

 others, which appeared to show that the animal body lost a slight 

 quantity of nitrogen by exhalation from the lungs. 



The statistical method would, therefore, appear to be one of the 

 most important aids towards a solution of some of the more 

 general questions in reference to the metamorphosis of the animal 

 tissues. We must, however, be careful not to deduce more from 

 such experiments than what is'permitted by the simplest induction ; 

 for the results derived from this method have unfortunately too 

 often been made to yield support to the vaguest fictions and the 

 boldest speculations. 



It need scarcely be observed that science should not rest satis- 

 fied with a knowledge of the final results of chemical processes in 

 the animal body, or with the assertion of the chemical dignity of 

 the vital process in summd, but should be made to enter more 

 deeply into the course of the separate processes, and into the 

 causal relations of phenomena. Here the statistical method cannot 

 of course afford any satisfactory solution to our enquiries ; for 

 when we have ascertained by this experimental method that fat is 

 formed in the animal body, we must learn from other methods the 

 manner in which this substance is formed. 



The method by which we may examine the course of phe- 

 nomena and the cause of their succession, might be named compa- 

 rative analytical or chemico-experimental, in as far as the chemical 

 phenomena of the living body may be artificially imitated, and 

 the chemical metamorphoses of certain substances external to the 

 vital sphere be compared with those within the influence of the 

 vital processes. Liebig and his school have here done essential 

 service. He was led to believe from his statistical enquiries on 

 fats, that these substances in their transmission through the 

 organism, were in a great measure oxidised and reduced to water 

 and carbonic acid, by which means they specially contributed 

 towards the maintenance of animal heat. As Liebig was by no 

 means inclined to believe, as some have supposed, that fat was 

 consumed in the lungs, somewhat in the same manner as oil burns 

 in a lamp, it was necessary more accurately to investigate its 



