VRi:\iiA 527 



of uremia in different eases are widely different; thus, if uremia is 

 due to complete suppression of urine through mechanical obstruction, 

 tlie symptoms 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 obstructive uremia, 

 the convulsions and other manifestations of nervous irritation charac- 

 teristic of uremia in eliroiiic nephritis being absent.'" 



Chemical Changes 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. That 

 there is an actual retention of organic substances in the blood in ure- 

 mia is shown conclusively, however, by the studies of the physico- 

 chemical properties of the blood. It has been repeatedly found that 

 in uremia the freezing-point of the blood is reduced markedly below 

 the normal; '^ instead of the normal depression of 0.55°-0.57° the 

 freezing-point is usually reduced more than — 0.60°, and sometimes 

 as nnich as — 0.75°, which shows that the number of molecules in the 

 blood is increased.^- At the same time, the electrical conductivity 

 may not be at all increased (Bickel),'^ but may even be reduced; 

 and as the electrical conductivity of the blood depends upon the num- 

 ber of dissociable molecules, chiefly inorganic salts, these are evi- 

 dently not increased. Therefore, the increased number of molecules 

 must represent an excess of organic molecules that dissociate but 

 little if at all, and hence are not conductors of electricity. Some 

 authors, indeed, have ascribed uremia to the increased osmotic pres- 

 sure of the blood from the retained molecules, but this is improbable, 

 according to Strauss,'* who found that a marked increase in molecu- 

 lar concentration may occur without uremia, and that we may have 

 a severe uremia without increased osmotic pressure.'^ 



Careful metabolic studies have shown that nephritics (chronic inter- 

 stitial) are not able to convert proteins into urea as rapidly or as 

 completely as normal persons.'" Erben ''^ has studied the variations 

 in the normal components of the blood during nei^hritis. and found 

 the albumin generally decreased in proportion to the globulin, espe- 

 cially in cases of parenchymatous nephritis; lecithin and calcium 

 are also decreased. Rowe '^'^ found the serum proteins greatly low- 



10 Chiari, however, observed true uremia, liotli clinical and aiiatomioal. in a 

 man with ureteral obstruction (Verh. Deut. Path. Gosell., 1!»12 [\'>) . 207). 



11 See Tieken, Amer. Med., 1905 (10). pp. .303. .507, and 822. 



12 See table of freezinfj points of blood and clfusions on page 35.5. 



13 Deut. med. Woch.. 1002 (28), 501. 



1-4 Die chronischen Nierenentziindungen. etc., Berlin, 1002. 



15 Stern (Med. Record, 1003 (63), 121) notes that the electrical eondtictivity 

 is reduced by the presence of excessive quantities of non-electrolytes in uremia, 

 and regards this lowered conductivity as a factor of some possiljle importance. 



i«Levene et al.. Jour. Exper. :Med.," 1000 (11), 825. 



I'Zeit. klin. Med.. 1003 (50), 441: 1905 (57), 30. 



17a Arch. Int. Med., 1017 (19), 3.54. 



