i EXCHANGE OF MATEEIAL 25 



and earthy sulphates arises from the combustion of protein, and 

 should therefore follow the same curve as that of the nitrogen. 

 The fact that the two curves are not absolutely parallel is probably 

 due to the two products not being eliminated as they are formed, 

 but retained to a greater or smaller extent by the blood according 

 to the degree of concentration of the plasma. 



The discharge of phosphorus in the form of phosphates enables 

 us to gauge the consumption during fasting of organic compounds 

 of phosphorus (lecithin, nuclein, jecorine) and the phosphates of 

 lime and magnesia in the bones. I myself in the case of Succi, 

 and Munk in that of Cetti, found that there was a relative increase 

 of phosphorus in proportion to the nitrogen. Munk found an 

 increase of both lime and magnesia, thus proving that the bones 

 also waste during fasting. I found further that the consumption 

 of phosphorus compounds economised the consumption of nitrogen. 

 As regards the output of chlorine, sodium, and potassium, 

 Munk found that during fasting there is a preponderance of 

 potassium over sodium, whilst on an ordinary diet the reverse 

 is the case, owing no doubt to the chloride of sodium with which 

 the food is flavoured. The chlorine, as in general also the 

 alkalies, decreases in the urine during fasting, and both are 

 retained in large quantities in the organism during the first few 

 days after food has been taken again, because of the deficiency of 

 these substances in the tissues. This is a proof that they are 

 real food substances, in the sense that they combine with the 

 organic molecules of the tissues and become structural materials. 



During the first days of nutrition after a long fast, the 

 organism clearly shows a tendency to compensate itself for the 

 losses it has suffered, by retaining a large quantity of protein, 

 fat, water, and salts. The young student, whose five days' fast 

 was studied by Tigerstedt, lost in that time 399 grins, of protein, 

 938 of fat, 3829 of water, and 37 of ash. In the two following 

 days on an ample diet he retained 20 per cent of the protein, 

 36 per cent of the fat, 71 per cent of the water, and 69 per cent 

 of the constituents corresponding to the ash lost during fasting. 



It is a very remarkable fact that the consumption of material 

 in the organism during fasting is not in proportion to the size 

 and weight of the fasting animal. The consumption per unit of 

 vveight differs considerably in small and large animals; the 

 smaller the animal, the greater is the consumption. If, on the 

 other hand, we reckon the consumption per unit of body-surface 

 instead of per unit of weight, we find, according to Bergmann and 

 Rubner, that the consumption corresponds to the body-surface. 

 This relation between consumption and body-surface is explained 

 according to Eubner by loss of heat. In order that the tempera- 

 ture of the body may remain constant, as is the case in warm- 

 blooded animals, the production of heat, and hence the organic 



