422 BLOOD AND LYMPH. 



the stroma, that is, of the portion of the corpuscle left after re- 

 moval of the hemoglobin. Such a large proportion of these two 

 substances is not found elsewhere in the body except in the myelin 

 sheath of the nerve fibers. It is believed that they play an impor- 

 tant role in maintaining the integrity of the corpuscles and 

 particularly in giving to the peripheral layer or membrane sur- 

 rounding the corpuscles certain characteristic properties of 

 permeability. Under normal conditions this external layer 

 is easily permeable to water and to certain substances in solution, 

 such as urea, alcohol, and ether, but it is said to be impermeable 

 to the neutral salts; the concentration of sodium chloride, for 

 example, is much greater in the plasma than in the red corpuscles. 

 The condition in which the hemoglobin exists within the cor- 

 puscle is not fully understood. It is evidently not in solution, 

 since the amount present is too great to be held in solution in 

 the corpuscle, and, moreover, even a thin layer of corpuscles 

 is far from being transparent. Nor is it deposited in the form 

 of crystals. It is assumed, therefore, that it is present in an 

 amorphous form. In Various ways, however, the relations of the 

 hemoglobin within the corpuscle may be disturbed; so that it 

 escapes and enters into solution in the plasma. Blood in which 

 this has happened suffers a change in color, becoming a dark 

 crimson, and is, therefore, known as "laked blood." Laked blood 

 in thin layers is quite transparent compared with the normal 

 blood with its opaque corpuscles. 



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 



