H^EMOLYSINS AND ALLIED BODIES 435 



lecithin to form a substance that is soluble in water. Others, like 

 ether and chloroform, probably directly dissolve out these sub- 

 stances. Cholesterin (and lecithin) being thus removed, the 

 permeability of the envelope is increased, and the normal, very 

 slight difference in molecular concentration between plasma and 

 corpuscular contents, become sufficient to determine diffusion of 

 the latter into the former. 1 Lecithin and cholesterin are normally 

 very insoluble in water, and no doubt form the most impervious 

 part of the envelope. 



In the case of biological poisons which we are about to 

 describe, the same explanation is possible ; something is changed 

 in the envelope so as to increase its permeability. Thus Baum- 

 garten has noticed that the first stage of haemolysis, as produced 

 by biological poison, is the swelling of the corpuscles, just as 

 occurs when the serum is made hypisotonic. He finds, further, 

 that heating hsemolytic serum to 55 C. does not in any way 

 influence its osmotic pressure (freezing-point and electrical con- 

 ductivity remain unaltered), whereas, as we shall see later, its- 

 haemolytic power is destroyed. We must suppose, therefore, 

 that the haemolysin affects the permeability of the envelope 

 perhaps by combining with the lecithin or cholesterin and the 

 slight an-isotonic condition of corpuscles and serum is then 

 sufficient to determine a diffusion of haemoglobin. By observing, 

 under a microscope, the behaviour of the nucleated erythrocytes 

 of amphibians towards specific haemolysins, it has been attempted 

 to determine whether, or not, haemolysin really kills the corpuscles. 

 The nucleus does not undergo destruction in the process (Landau 3 ), 

 so that it would appear as if the permeability of the envelope 

 had alone been affected. 



Haemolysis may also be produced by an entirely different 

 cause than that described above, viz. by the disturbance of the 

 osmotic equilibrium of the plasma and corpuscles. So long as 

 the osmotic pressure of the fluids in which the corpuscles are 

 suspended is almost the same as that of the corpuscular contents 



1 As Stewart ( 2 ) has pointed out, blood "lakers" are divided into two groups, 

 according to whether they cause the haemoglobin alone to leave the corpuscle 

 mild lakers, e.g. haemolytic sera, freezing and thawing or also cause inorganic 

 salts, i.e. electrolytes, to be extracted severe Inkers, e.g. heat, water, &c. The 

 latter group cause the electrical conductivity of the suspending medium (serum) 

 to be increased when hgemolysis is produced, the former cause no such increased 

 conductivity. 



