PROTEIN REQUIREMENTS 



In each case within the number of days indicated the nitrogen out- 

 put had returned to the original level. 



Apparently, then, in addition to the splitting of the protein molecule 

 into a nitrogen-rich and a nitrogen-free portion, there is a like separa- 

 tion of the sulphur-containing fraction. The early breakdown of the 

 sulphur combination may also account for the rapid increase in the out- 

 put of carbon dioxide which has also been observed after the ingestion of 

 food (Frank and TrommsdorfT 1 34). 



Examination of the Nitrogen : Phosphorus Ratio. 



The rate of the output of phosphorus has also been frequently 

 compared with that of the. nitrogen output. It has been found that 

 the phosphorus output does not bear the same intimate relation to the 

 rate of protein catabolism that sulphur does. This is not a matter 

 for surprise, as in all probability the phosphorus, or the greater part 

 of it, is associated with the special nucleo-proteins of the food and 

 the tissues, and may undergo a special form of catabolism. As will 

 be shown later in discussing the course of catabolism during fasting, 

 nucleo-proteins apparently are more resistant to the action of pro- 

 teolytic enzymes than the ordinary tissue protein. The curve of the 

 phosphorus excretion has been found to run more or less parallel to 

 the nitrogen curve, but behind it. The output of phosphorus has been 

 investigated by Sherman and Hawk (371 A), Siven (374), Ehrstrom 

 (no), Tigerstedt (397), Hamalainen and Helme (167), and others. 



