418 NUTRITION. 



grammes as urine and faeces, and 0*55 of a gramme through other 

 channels. 



If we calculate from Barral's experiments the distribution 

 which 100 grammes of absorbed carbon undergo in its excretion 

 after it has fulfilled its functions in the organism, we shall find that 

 (in an adult man) 91*59 grammes pass into the products of perspi- 

 ration, and only 4*58 grammes into the urine, and 3*83 grammes 

 into the faeces. According to this estimate, more than nine-tenths 

 of the carbon contained in the food are entirely consumed and con- 

 verted into carbonic acid. 



If we pursue a similar method of inquiry in reference to the 

 mode of excretion of nitrogen, and follow the experiments which 

 Barral instituted on his own person, we arrive at the following 

 results : (the nitrogen in the food taken by Barral being to the 

 carbon as 1 : 12*8 ;) for every 100 parts of absorbed nitrogen only 

 8-33 parts were again excreted with the faeces, while 42'07 parts 

 were given off with the urine, and49'6 parts through the skin and 

 lungs. The relative amount of the nitrogen eliminated by the per- 

 spiration is here excessively large, and entirely at variance 

 with the experiments which many other investigators have made 

 on animals. 



It further appears from the above table, that for every three 

 parts by weight of solid and fluid food (that is to say, such food as 

 Barral used during the prosecution of his experiments, and which 

 consisted on an average of 25'15-u- of solid substances), about one 

 part by weight of oxygen entered into the metamorphosis of matter. 

 The water which was separated through the lungs and skin 

 amounted in all the cases (excepting that of the man aged fifty-nine 

 years,) to somewhat more than the quantity which was discharged 

 by the sensible excretions. It follows, moreover, from these experi- 

 ments, that an adult man oxidises on an average 289*0 grammes 

 of carbon, and 18'6 grammes of hydrogen, in the twenty-four 

 hours. 



However carefully these investigations may appear to have 

 been conducted, they yet can only serve as examples of the manner 

 in which the consumption of matter occurs under different rela- 

 tions in the human organism ; but as very many conditions which 

 exert an essential influence on vegetative life must be wholly dis- 

 regarded, and as, moreover, the method of investigation does not 

 exclude all doubt of the accuracy of the results even in special 

 cases, these very meritorious labours can scarcely for these reasons, 

 and in consequence of their isolated character, be of any great ser- 



