532 A MANUAL OF PHYSIOLOGY 



been reduced to 4 grammes. It is a remarkable fact that 

 while a mixture of carbo-hydrate and fat will act just as well 

 as carbo-hydrate alone in bringing about this reduction in the 

 nitrogen output, fat without carbo-hydrate is much less effec- 

 tive. The hypothesis has been suggested that the cells must 

 have some sugar, and that when fat alone is given, a portion of 

 the body-protein, which would otherwise have been saved, is 

 broken down to supply the necessary sugar (Landergren). 



The results obtained on fasting men differ in some respects 

 from those obtained on starving animals. In ten days of hunger, 

 Cetti, a professional ' fasting man ' of meagre habit, excreted 

 112 grammes nitrogen, or an average of n grammes a day. 

 The excretion was least on the eighth, ninth, and tenth days 

 namely, about 9 grammes a day. On the third day it was 

 higher than on the second, and almost as high on the fourth as 

 on the third. A similar rise in the nitrogen excretion on the 

 second day has been observed in other fasting men, but is 

 either rare or absent in fasting dogs. The explanation appar- 

 ently is that in the ordinary food of man there is a greater 

 abundance of carbo-hydrates and fats, the protein-sparing action 

 of which is most pronounced at the very beginning of the starva- 

 tion period. The quantity of chlorine and alkalies in the urine 

 was also diminished,, while the phenol was increased. The 

 respiratory quotient sank to o - 66 to 0*69 even less than the 

 quotient corresponding to oxidation of fats alone. The mean- 

 ing of this, in all probability, is that some of the carbon of the 

 broken-down proteins was laid up in the body as glycogen 

 (Zuntz). In another professional fasting man (Succi) with a 

 considerable amount of body-fat, the excretion of nitrogen was 

 found to diminish continuously during a fast of thirty days, 

 being less than 7 grammes on the tenth day. In another fast of 

 21 days by the same person it was a little less than 3 grammes 

 on the last day. The surprisingly small nitrogenous waste in 

 this case is perhaps to be accounted for by the protein-sparing 

 action of the abundant body-fat. The nitrogenous metabolism 

 has also been investigated during long-continued hypnotic sleep 

 (Hoover and Sollmann). The results were very much the same 

 as in an ordinary starvation experiment. 



It might be supposed that if an animal was given as much 

 nitrogen in the food in the form of proteins as corresponded 

 to its daily loss of nitrogen during starvation, this loss would 

 be entirely prevented, and nitrogenous equilibrium restored. 

 The supposition would be very far from the reality. If a dog 

 of 30 kilos weight, which on the tenth day of starvation excreted 

 11-4 grammes urea, had then received a daily quantity of protein 



