CHAP, v.] NUTRITION. 445 



which agrees very closely with the 17*6 p. c. lost by the blood. It 

 is worthy of remark that the tissues in general became more 

 watery than in health. We might infer from these data the con- 

 clusions that metabolism is most active first in the adipose tissue, 

 next in such metabolic tissues as the hepatic cells and spleen-pulp, 

 then in the muscles, and so on; but these conclusions must be 

 guarded by the reflection that because the loss of cardiac and 

 nervous tissue was so small, we must not therefore infer that their 

 metabolism was feeble; they may have undergone rapid metabolism, 

 and yet have been preserved from loss of substance by their 

 drawing upon other tissues for their material. 



During this starvation-period, the urine contained in the form 

 of urea (for, as we shall see, the other nitrogenous constituents of 

 urine may for the most part be disregarded) 277 grammes of 

 nitrogen. Now the amount of muscle which was lost during the 

 period contained about 15'2 of nitrogen. Thus, more than half 

 the nitrogen of the output during the starvation-period must 

 have come ultimately from the metabolism of muscular tissue. 

 This is an important fact of which we shall be able to make use 

 hereafter. Bidder and Schmidt came to the conclusion, from their 

 observations on a starving cat, that the quantity of urea excreted 

 per diem, in all but the earlier days of the inanition period, bore a 

 fixed ratio to the body- weight. In the first two or three days of the 

 period, the daily quantity of urea was much in excess of this ratio. 

 They were thus led to distinguish two sources of urea : a quantity 

 arising from the functional activity of the whole body, and therefore 

 bearing a fixed ratio to the body-weight, and continuing until near 

 the close of life ; and a quantity arising from the amount of surplus 

 nitrogenous or proteid material which happened to be stored up in 

 the body at the commencement of the period, and which was 

 rapidly got rid of. The latter they regarded as not entering 

 distinctly into the composition of the tissues, but as, so to speak, 

 floating capital, upon which each or any of the tissues could draw. 

 They spoke of its direct metabolism as a luxus consumption. More 

 extended observations however have shewn that though the urea 

 of the first two or three days much exceeds that of the subsequent 

 days of a starvation-period, no such fixed relation of urea to body- 

 weight as that suggested obtains. To the question of a luxus con- 

 sumption we shall have again to refer. 



The Normal Diet. What is the proper diet for a given animal 

 under given circumstances, can only be determined when the laws 

 of nutrition are known. Meanwhile it is necessary to gain an 

 approximate idea of what may be considered as the normal diet 

 for a body such as that of man under ordinary circumstances. 

 This may be settled either by taking a very large average, or by 

 determining exactly the conditions of a particular case. In the 

 table below is given both the average result obtained by Moleschott 

 from a large number of public diets, and the diet on which an 



