METHODOLOGICAL INTRODUCTION* 17 



processes as they occur in the living body, since we are here as 

 little able to call forth the necessary conditions and relations, as in 

 the formation of minerals and rocks. It is, therefore, the more 

 necessary to observe a process, of which we cannot judge by imita- 

 tion, in its course in the living body, and for this end we must 

 chiefly employ natural physiological means. Among these we may 

 reckon the investigations that have been made in reference to 

 the contents of the stomach during the process of natural 

 digestion, to the chemical change of individual substances in 

 the development of the egg during incubation, and to the de- 

 pendence of the products of respiration on different external 

 conditions. We may further add those experiments that have 

 been made on the changes of individual substances during 

 their passage through the animal organism, or on the effect 

 of different kinds of food, and the metamorphoses of certain 

 nutrient substances during the process of nutrition. To the same 

 method belong all pathologico-chemical experiments, as for in- 

 stance, observations on the contents of the intestine after the closure 

 of the common bile duct, and on the blood and other fluids after 

 extirpating or tying the vessels of the kidneys. Chemistry, unfor- 

 tunately, too often fails us to permit of our deriving from this 

 method all the results which it appears to promise; it must 

 however, ultimately furnish the key- stone to all physiologico- 

 chemical enquiries, which, without its aid, would continue insoluble 

 enigmas, and would admit of hypothetical rather than actual 

 explanation. The theory of the metamorphosis of animal matter, 

 without the support of such a physiologico-experimental founda- 

 tion, must continue to be attended by no little risk. 



In conclusion, we would advance a few remarks on the place 

 which physiological chemistry occupies, or at some future period will 

 occupy, among the auxiliary medical sciences. If the final result 

 of all physiologico-chemical enquiries be that of comprehending 

 the chemical phenomena of animal life in their different phases 

 and in their causal connexions, it is obvious that we must look to 

 this science for a solution of the most important questions of 

 physiology, and of medicine generally. It cannot be denied that 

 most of the phenomena of animal life either consist in or are 

 accompanied by chemical processes ; nor can we form an adequate 

 conception of the functions of the nervous system by which 

 sensuous perception and motion are regulated, without the simul- 

 taneous existence of chemical actions. For although we are as yet 

 unable to make nervous action fully harmonise with definite 



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