154 NUTRITIONAL PHYSIOLOGY 



apparently of no further use in the system. It is destined 

 to circulate until it shall find its way into the urine. The 

 efficiency of the kidneys is so remarkable and the whole 

 blood volume is carried through them at such short in- 

 tervals that the percentage of urea in normal blood is 

 kept very low. Urea seems to be a most convenient form 

 for nitrogen elimination; it is highly soluble and diffusible, 

 inert, and, comparatively speaking, non-poisonous. If 

 a man eats 100 grams of protein in twenty-four hours he 

 will excrete some 30 grams of urea, an amount which rep- 

 resents about seven-eighths of the total nitrogen passing 

 into and out of the body.__ This urea is not all made by the 

 liver, but a large share of it proceeds from the deaminizing 

 activities of this organ. 



What, then, is the principal non-nitrogenous compound 

 produced from the amino-acids in the liver? There seems 

 to be no doubt that it is dextrose. Evidence in support of 

 this belief has been derived from the study of diabetes. 

 Whether this condition is experimentally induced or devel- 

 ops spontaneously, it is found that, if the case is one of full 

 severity, sugar excretion goes on even when no carbohy- 

 drate is fed, and, indeed, throughout long periods of fast- 

 ing. This sugar might be assumed to have come from the 

 fat of the body, but it can be more surely attributed to the 

 protein which is being decomposed. The following con- 

 sideration shows this: the nitrogen and the sugar in the 

 urine of the fasting diabetic patient maintain a singularly 

 constant ratio; 1 gram of nitrogen is accompanied by 3.6 

 grams of dextrose. They rise and fall together. This 

 seems to prove that the two must have a common source, 

 which can only be protein. Again, the feeding of amino- 

 acids to the diabetic increases his loss of sugar; the feeding 

 of fat does not have this effect. A simple calculation 

 shows that 100 grams of protein fed may give rise within 

 the body to about 57 grams of sugar. The seriousness of 

 diabetes will now be better appreciated than has been 

 possible up to this time. The organism loses not merely 

 the support normally secured from the chief carbohydrates 



