GENERAL PROPERTIES: THE CORPUSCLES. 397 



disturbed; so that it escapes and enters into solution in the plasma. 

 Blood in which this has happened suffers a change in color, be- 

 coming 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. 



HetootySis. The act of discharging the hemoglobin from the 

 corpuscles so that it becomes dissolved in the plasma is designated 

 as hemolysis, and substances 1 that cause this action are spoken of 

 as herrttrtytic 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 adding bile or solutions of the bile 

 salts. (4) By adding amyl-alcohol. (5) By adding the serum 

 from the blood of certain animals. (6) By adding saponin or 

 sapo toxin. (7) By the addition of an excess of alkali. (8) 

 By various toxins found in snake venom or in the serum of other 

 animal^ or among the products of bacterial activity (natural 

 hdmolysins) or by similar organic substances produced within the 

 body by the process of immunizing. Two of these methods de- 

 mand especial mention, as they involve the consideration of proc- 

 esses of great physiological importance. 



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 discharge and dissolve 

 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 destroyed. Solutions whose osmotic pressure 

 is the same as that of the plasma are said to be isosmotic or iso'toriic 

 with the blood, those whose pressure is lower are designated as 



