METABOLISM IN NEPHRITIS 337 



urea in the blood is a measure of the nitrogen balance for that individual's 

 entire life. It is making a big effort with very little result to perform 

 all the steps required to test out the nitrogen balance, by the older pro- 

 cedure of measuring intake and output over several days when a single 

 chemical procedure furnishes a much more accurate answer. 



Possibly more space than necessary has been devoted to the discussion 

 of the nitrogen balance in nephritis than is warranted. However, it may 

 be of some value to understand the various pitfalls which the clinician 

 who employs this method of observation may >meet with, and further- 

 more, it is very important to make clear that blood chemistry has to a 

 very great extent supplanted quantitative urine analyses. This one phase 

 of urinary examination has been gone into in some detail so as to make the 

 points brought forward clear ; other aspects of quantitative urine analyses, 

 as far as they are of importance to metabolism, will be taken up under 

 renal function, but the stress that was formerly accorded the 24 hour bal- 

 ance of all the materials normally found in the urine is out of place, since, 

 just as for nitrogen, the examination of the blood furnishes a much bet- 

 ter criterion than the comparative estimation of intake and output. 



Protein Destruction in Nephritis 



It has been assumed for some time that protein destruction plays a part 

 in Bright' s disease. Senator believed that it occurred in uremia ; Von 

 Noorden and Richter each reported one case in which an excessive elimi- 

 nation of nitrogen as compared to the food intake was supposed to indicate 

 that a disintegration of body tissue had taken place. No one was really 

 in a position to be certain of his ground in regard to this problem until 

 the microchemical methods were successfully applied to the determination 

 of the non-protein nitrogen of the blood. With this added source of infor- 

 mation, not only can the intake and output of nitrogen be estimated, but 

 also the course of intermediate metabolism (see section on the nitrogen bal- 

 ance in nephritis) can be gauged. All of these three factors must neces- 

 sarily be known if occurrence of protein destruction is to be definitely 

 demonstrated. 



It is interesting to note that protein destruction may occur in a variety 

 of conditions. Intestinal obstruction, the presence of a closed intestinal 

 loop, the injection of toxic proteose, may all bring it about (Whipple and 

 Cooke). In these instances a heaping up of nitrogen in the blood, while 

 its excretion in the urine is increased, can only be explained on the basis 

 of an augmented protein catabolism. Plasmaphoresis entails a similar 

 injury to body protein ( Kerr, Hurwitz and Whipple(a) (6) ). This is sup- 

 posedly due to marked dilution of the plasma. It suggests the possibility 

 that the same phenomenon may take place if edema comes on very rapidly. 



