244 THE BLOOD 



2. Physical, freezing and thawing, heat, condenser discharges, etc. 



3. Endosmosis, dropping blood into water or into a hypo-tonic 

 solution. 



4. Exosmosis (see crenation), dropping blood into a hypertonic 

 solution. 



5. Action on Lipoid constituents of capsule. 



i. Anaesthetics are lipoid solvents. 



ii. Bile salts and pigments affect permeability of lipoid 

 membranes. 



iii. Glucosides, e.g. saponin are adsorbed by the membrane 

 (Willard Gibbs' Law), because they lower surface 

 tension. They then insert themselves into the texture 

 of the membrane and increase its permeability (see 

 p. 111). 



6. Biological Agents. 



i. Toxins of certain bacteria produce haemolysis, e.g. 



tetanolysin of B. Tetani ; megatheris lysin of B. 



Megatherium ; toxic lysins of staphylococcus and 



B. pyocyaneus. 

 ii. Cobra and rattlesnake venom cause laking both in vivo 



and in vitro. 

 iii. The serum of one animal is often haemolytic for the 



blood of a different species, 

 iv. Certain phyto-albumins, e.g. abrin, ricin, and robin 



produce haemolysis. 



7. Chemical Agents. 



Haemolysis may be caused by the ingestion or injection of 

 certain drugs, e.g. chlorates, nitrites, nitrobenzene, aniline deriva- 

 tives (e.g. acetanilide and phenacetin) quinine. These, generally, 

 partially convert the haemoglobin into methaemoglobin (q.v.). 



The laking of blood thus depends on altering the permeability 

 of the stroma or capsule of the erythrocyte. Normally this 

 membrane is impermeable to colloids and to most crystalloids. 

 This has been determined by estimating the electrical conduc- 

 tivity of blood before and after laking. The corpuscles hinder 

 the passage of small electrical charges because their walls are 

 impermeable to ions carrying the charge. On rupturing the 

 membranes these ions get a free passage and the conductivity of 

 the blood increases. That this increase is not due to the liberation 

 of haemoglobin may be shown by fixing the corpuscles with for- 

 malin which prevents the egress of the pigment but not of the salts. 



