446 THE STATISTICAL METHOD. [Boon-it 



observer (Ranke) found himself in good health, neither losing nor 

 gaining weight. 



Public Diet (Moleschott). Eanke. 



Proteids 30 100 



Fat 84 100 



Amyloids 404 240 



Salts 30 25 



Water 2800 2600 



Of these two diets, which agree in many respects, that of 

 Rarike is probably the better one, since in public diets, the cheaper 

 carbohydrates are used to the exclusion of the dearer fats. 



Comparison of Income and Output. 



Method. We have now to inquire how the elements of such a 

 diet are distributed in the excreta, in order that, from the manner 

 of the distribution, we may infer the nature of the intermediate 

 stages which take place within the body. By comparing the 

 ingesta with the excreta, we shall learn what elements have been 

 retained in the body, and what elements appear in the excreta 

 which were not present in the food ; from these we may infer the 

 changes which the body has undergone through the influence of 

 the food. 



In the first place, the real income must be distinguished from 

 the apparent one by the subtraction of the faeces. We have seen 

 that by far the greater part of the faeces is undigested matter, i. e. 

 food which, though placed in the alimentary canal, has not really 

 entered into the body. The share in the faeces taken up by matter 

 which has been excreted from the blood into the alimentary canal, 

 is so small that it may be neglected; certainly with regard to 

 nitrogen, the whole quantity of this element, which is present in 

 the faeces, may be regarded as indicating simply undigested nitro- 

 genous matter. 



The income, thus corrected, will consist of so much nitrogen, 

 carbon, hydrogen, oxygen, sulphur, phosphorus, saline matters, and 

 water, contained in the proteids, fats, carbohydrates, salts, and 

 water of the food, together with the oxygen absorbed by the lungs, 

 skin, and alimentary canal. The output may be regarded as 

 consisting of (1) the respiratory products of the lungs, skin, and 

 alimentary canal, consisting chiefly of carbonic acid and water, 

 with small quantities of hydrogen and carburetted hydrogen, these 

 two latter coming exclusively from the alimentary canal ; (2) of 

 perspiration, consisting chiefly of water and salts, for the dubious 

 excretion (see p. 386) of urea by the skin may be neglected and 



