420 BLOOD AND LYMPH. 



Hemolysis.- — The act of discharging the hemoglobin from the 

 corpuscles so that it becomes dissolved in the plasma is designated 

 as hemolysis, and substances that cause this action are spoken of 

 as hemolytic agents. A number of such agents are known; but, 

 although the results of their action are the same, so far as the hemo- 

 globin is concerned, the way in which they bring about this result 

 must vary greatly. Some of the known methods of producing 

 hemolysis, or rendering the blood "laky," are as follows: (1) 

 By the addition of water to the blood or by diminishing in any way 

 the concentration or osmotic pressure of the plasma. (2) By add- 

 ing ether or chloroform. (3) By the addition of soaps or of the 

 higher fatty acids, especially the unsaturated acids. (4) By 

 adding bile or solutions of the bile-salts. (5) By adding amyl- 

 alcohol. (6) By adding the serum from the blood of certain 

 animals. (7) By adding saponin or sapotoxin. (8) By the 

 addition of an excess of alkali. (9) By various toxins found in 

 snake venom or in the serum of other animals or among the prod- 

 ucts of bacterial activity (natural hemolysins), or by similar or- 

 ganic substances produced within the body by the process of im- 

 munizing. Some of these hemolytic agents, such as ether, bile 

 salts, and soaps, probably effect their action by their power of 

 uniting with the lipoid elements (lecithin, cholesterin) in the 

 stroma of the corpuscles. The framework of the corpuscles is 

 thus altered so that the hemoglobin is set free. The action of the 

 hemolysins and of agents which lower the osmotic pressure of the 

 plasma demands a more detailed description, as processes of great 

 practical importance are involved in these changes. 



Hemolysis Caused by Lowering the Osmotic Pressure of the Plasma. 

 — The blood corpuscles contain a certain amount of water ( 57 to 

 64 per cent.), an amount insufficient to discharge the hemoglobin. 

 We may imagine that the osmotic pressure within the corpuscle is 

 such, compared with the osmotic pressure exerted by the salts in 

 the plasma, that a water equilibrium is established, and that, 

 although water molecules diffuse into and out of the corpuscle, 

 the exchange is equal in the two directions. If, however, the 

 outside plasma is diluted by the addition of water to any consider- 

 able extent, then the osmotic pressure outside the corpuscles is 

 correspondingly reduced, while that within the corpuscles is 

 unchanged. Consequently an increased amount of water will 

 pass into the corpuscles, sufficient, in fact, to '•upture the cor- 

 puscles and thus discharge the hemoglobin. It is evident, 

 therefore, that in injecting liquids into the circulation or in 

 diluting blood outside the body care must be taken not to use 

 solutions whose osmotic pressure is markedly less than that of 

 blood-plasma, otherwise many of the red corpuscles may be 



