UREMIA 435 



between the portal vein and the inferior vena cava, the blood 

 from the portal system then passing directly into the general 

 circulation without first passing through the liver. In such 

 animals the urine becomes poor in urea and relatively rich in 

 ammonium carbamate. At the same time, the dogs show severe 

 symptoms of intoxication from which they die, and which are 

 similar to the symptoms that follow intravenous injection of 

 ammonium carbamate. Ammonium carbamate, being a sub- 

 stance of considerable toxicity l when free in the blood, it has, 

 therefore, been quite widely considered that it may be an 

 important factor in the production of uremic symptoms. On the 

 other hand, it seems most probable that the condition of uremia 

 does not depend upon one but upon many various and vary- 

 ing substances. Clinically the symptoms of uremia in different 

 cases are widely different ; thus, if uremia is due to complete 

 suppression of urine through mechanical obstruction, the symp- 

 toms are quite different from those observed in the uremia 

 following a chronic nephritis ; drowsiness, weakness of heart 

 action, and syncope being the chief manifestations of obstruc- 

 tive uremia, the convulsions and other manifestations of nervous 

 irritation characteristic of uremia in chronic nephritis being 

 absent. 



Chemical Change in Uremia. The attempts to isolate 

 from the blood and organs of uremic patients or animals toxic 

 substances that explain the manifestations of uremia have thus 

 far failed. 2 That there is an actual retention of organic sub- 

 stances in the blood in uremia is shown conclusively, however, 

 by the studies of the physicochemical properties of the blood. 

 It has been repeatedly found that in uremia the freezing-point of 

 the blood is reduced markedly below the normal; 3 instead of 

 the normal depression of 0.55 0.57 the freezing-point is 

 usually reduced more than 0.60, and sometimes as much 

 as .75, w T hich shows that the number of molecules in 

 the blood is increased. 4 At the same time, the electrical 

 conductivity may not be at all increased (Bickel 5 ), but may 

 even be reduced ; and as the electrical conductivity of the 

 blood depends upon the number of dissociable molecules, 

 chiefly inorganic salts, these are evidently not increased. 

 Therefore, the increased number of molecules must represent 



1 See Bickel, " Exp. Untersuch. iiber Cholaemie," Wiesbaden, 1900. 

 2 SeeCouve"e, Zeit. klin. Med., 1904 (54), 311. 



3 SeeTieken, Araer. Med., 1905 (10), pp. 393, 567, and 822; complete liter- 

 ature. 



4 See table of freezing points of blood and effusions on page 298. 

 5 Deut. med. Woch., 1902 (28), 501. 



