HEMOinaiAdE 295 



capillary walls suffering from lack of nourisliiiicnt, even with the 

 poorest of blood, and it seems more probable that the hemorrhages are 

 due, even in cachexia, to chemical constituents of the blood that in- 

 jure the endothelium. Hemorrhages that follow re-establishment of 

 the circulation after complete occlusion, however, may be the result 

 of asphyxial clianges in the capillary walls, presumably colloidal swell- 

 ing of the cells. 



After severe hemorrhages the blood shows a decrease in specific 

 gravity and viscosity, an increase in surface tension and electrical 

 resistance, and either increase or decrease of the freezing-point de- 

 pression, all these changes being transient if the individual is other- 

 wise normal.'^ (See also Secondary Anemia.) There is a rapid 

 absorption of fluid from the tissues and tissue spaces, resulting in a 

 dilution of protein and formed elements, but not of salts. For the 

 same reason the density of the blood decreases in direct relation to the 

 proportion of the total blood that has been lost.-^ The alkali reserve 

 of the blood is somewhat lowered by severe hemorrhage, ^^ but there is 

 not a marked acidosis. The total nitrogen of the blood of course 

 falls, but there is a tendency for sugar, urea and non-protein N to 

 increase, and there is increased elimination of creatine in the urine, 

 presumably from destruction of muscle tissue to replace the lost blood 

 proteins. There is said to be a decreased permeability of vessels, 

 resulting in reduced exudative processes. ^^ The proportion of the 

 several blood proteins is variably altered after repeated hemorrhages; 

 the sugar is little affected^^ but there may occur a marked rise in the 

 content of immune bodies, especially specific agglutinins.^^ Rapid 

 hemorrhages cause a decrease in the coagulation time because of a 

 decrease in antithrombin and a slight increase in prothrombin, in 

 spite of a decrease in fibrinogen.-^ If the blood is withdrawn re- 

 peatedly in large amounts, centrifuged, and the washed corpuscles 

 reinjected suspended in isotonic salt solution (plasmaphaeresis), life 

 can be maintained even after 4 to 5 times the total volume of blood 

 has been removed and washed. This is possible because of rapid 

 reformation of the plasma, and the blood shows the changes characteris- 

 tic of secondary anemias. ^^ Lipemia is often produced by severe or 

 repeated hemorrhages, with a great increase in the phospholipins of 

 the plasma and corpuscles. ^^^ 



Changes in the Extravasated Blood. — These begin soon after 

 its escape. In most situations sufficient fibrin ferment is formed to 



" Oliva, Folia clinica, 1912 (3), 213. 



"Richet et al, Compt. Rend. Acad. Sci., 1918 (166), 587. 



2<Buell, Jour. Biol. Chem., 1919 (40), 29; Tatum, ibid., 1920 (-41), 59. 



"Luithlen, Med. Klin., 1913 (9), 1713. 



26 Taylor and Lewis, Jour. Biol. Chem., 1915 (22), 71. 



''^ See Hahn and Langer, Zeit Immunitat, 1917 (26), 199. 



28 Drinker, Ainer. Jour. Phvsiol., 1915 (36), 305. 



29 Abel et al, Jour. Pharmacol., 1914 (5), 625; 1915 (7), 129. 

 29"Bloor and Farrington, Jour. Biol. Chem., 1920 (41) xlviii. 



