CHAPTER XIX 



THE FORMATION OF UREA 



UREA or carbamide, CO . (NH 2 ) 2 , is in mammals the form in which 

 the major part of the nitrogen absorbed from the alimentary 

 canal leaves the body in the urine. The proportion of the 

 total urinary nitrogen excreted as urea and other substances is 

 by no means constant even in health. The following table 

 shows the effect produced upon the distribution of the urinary 

 nitrogen in a healthy man by altering the total nitrogen of 

 the food. 



Quantity of urine . 1170 c.c. 385 c.c. 



Total nitrogen . . 16'8 grm. 36 grm. 



Urea-nitrogen . . 147 grm. = 87'5% 2-2 grm. =61-7% 



Ammonia-nitrogen . 0'49 grm. = 3'0% 0'42 grm. = 11-3% 



Uric-acid nitrogen . 0-18 grm. = M% 0'09 grm. - 2-5% 



Kreatinin-nitrogen . "58 grm. = 3'6% O60 grm. = 17'2% 



Undetermined nitrogen 0-85 grm. = 4*9% 0'27 grm. = 7'3% 



Total SO 3 . . . 3-64 grm. 076 grm. 



Inorganic S0 3 . . 3'27 grm. = 90'0% 0'46 grm. = 60'5% 



Ethereal SO 3 . . 0'19grm.= 5-2% 0-10 grm. = 13'2% 



Neutral SO 3 . . 0-18grm.= 4-8% 0'20 grm. = 26'3% 



(Folin.) 



It will be seen that when the total urinary nitrogen has been 

 greatly reduced the nitrogen excreted as urea falls to about 

 60 per cent, of the whole, and that there is a corresponding rise 

 in the nitrogen excreted as ammonia, kreatinin, and undetermined 

 bodies and also in the excretion of neutral sulphur. On a liberal 

 nitrogenous diet the urea-nitrogen forms at least 85 per cent, 

 of the whole. 



The problem to be discussed is, what tissues produce urea 

 and out of what do they form it. 



According to the theories both of Voit and of Pflliger the 

 bulk of the nitrogen of the food after absorption is built up either 

 into proteid or into bioplasm, and this is broken down in 



