METABOLISM IN NEPHRITIS 387 



It has been suggested by no less an authority than Rosenstein, that 

 uremia must have a multiple etiology because of the diversity of its symp- 

 toms. This does not agree with the explanation of urinary insufficiency as 

 the sole cause, offered in the preceding paragraph. (Cohnheim then goes 

 on at length to show how the various forms of uremia are all due to re- 

 tention of products ordinarily excreted by the kidney; inasmuch as 

 we now know from studies in blood chemistry that this is not so, this part 

 of Cohnheim's discussion is omitted. The subject will be taken up in 

 greater detail, and from the more recent viewpoint, in the next section.) 



Cohnheim attempted to ascribe all the conditions that had been de- 

 scribed as uremia to one factor, renal insufficiency. The reasoning was 

 excellent as far as it could go at that time, and was correct from the 

 point of view that every instance of renal insufficiency may result in 

 uremia; but the converse, that every case of uremia is due to inadequate 

 kidney function is not true. What is to-day frequently considered to be 

 uremia may be divided into three groups, as already outlined in the intro- 

 duction. 



1. Those conditions whose symptomatology resembles that of uremia, 

 but whose occurrence is not dependent upon nor necessarily associated 

 with diseases of the kidney. 



2. The symptom complex depending upon renal insufficiency, which 

 has also been called retention uremia (Foster(a), 1916). 



3. The clinical picture whose manifestations apparently depend prin- 

 cipally upon an irritation of the central nervous system ; it accompanies 

 the various forms of Bright's disease but is not dependent upon renal in- 

 sufficiency. 



Conditions Hitherto Often Erroneously Classified as Uremia. It is now 

 recognized, largely through the efforts of Sir Clifford Allbutt(a), that in- 

 creased arterial pressure is not necessarily dependent upon renal disorders 

 but is in many instances an independent disease. (See section on blood 

 pressure.) This condition, which has been most commonly known as es- 

 sential hypertension, entails, among other changes, arteriosclerotic lesions 

 in the cerebral blood vessels. These in turn can produce areas of soften- 

 ing and hemorrhages in the brain tissue. Vomiting, palsies, temporary or 

 permanent, convulsions, coma, etc., are often due to such anatomical 

 changes and not to some mysteriously elaborated poison. There had been 

 only one alternative offered as an explanation of these manifestations, and 

 that is that temporary anemia brought on by arterial spasm may be respon- 

 sible. Osier and Pal have been particularly enthusiastic in advocating this 

 possibility. 



