THE NORMAL QUANTITY OF FOOD. 411 



proposition is so clear, and is proved by such numerous facts in 

 our daily experience, that it would be superfluous to enter more 

 fully into this subject; we will only observe that in addition to the 

 above-indicated standard, a special standard might also be estab- 

 lished for the consumption required during a period of bodily 

 labour, and that, in addition to these, many other relations involve 

 differences in the requirements of nutrition. 



In all these cases, we have proceeded on the assumption that 

 we are considering an organism which has attained its full develop- 

 ment, in which, therefore, the absolute weight of the living object 

 remains the same, so that the excreta can be accurately balanced 

 by the ingesta. There is still greater difficulty in deciding the 

 question regarding the absolute extent of the requirements of 

 nutrition when growth, corpulence, or pregnancy, and similar rela- 

 tions in which there is an increase of weight, have to be considered ; 

 in these cases the excreta fall below the ingesta, and hence the 

 latter cannot furnish any conclusions regarding the quantity of the 

 nutrient matters which are necessary for the due accomplishment 

 of these physiological functions. Boussingault was here as 

 throughout the whole of this department of inquiry, the first to 

 lead the way, and he instituted a numerous series of investigations 

 which have already yielded the most brilliant results. Yet not- 

 withstanding all these investigations we have hitherto failed in 

 establishing any sharply defined determinations of the amount of 

 food necessary to the organism under certain given relations. How- 

 ever much we may have learnt from the laborious researches of 

 different inquirers, we are still entirely wanting in the exact normal 

 determinations, to which we had hoped to attain in this depart- 

 ment of science. 



The sketch which we have here given of the experiments made 

 to determine the necessary amount of food could only serve as an 

 introduction to further considerations of the actual phenomena of 

 nutrition ; while at the same time it might indicate the direction 

 by which we might most securely traverse the still mysterious 

 labyrinth of ever varying phenomena. It might not be out of place 

 if, before we passed to the special statistics of the metamorphosis of 

 animal matter, we were once more to revert to the limit which the 

 resorptlon of nutrient matters from the intestine cannot exceed, 

 and which consequently appertain to nutrition and the metamor- 

 phosis of matter. Although this subject has frequently been touched 

 upon in the course of this work, we have deferred to the present 

 moment entering more fully into this question, as it has the most 



