HAEMOLYSIS 245 



Laked blood has a lower viscosity than whole blood due to the 

 pseudo-viscosity caused by the corpuscles. 



Haemolysis by freezing and thawing. 



It has been noticed that blood could be repeatedly frozen and 

 thawed as in the determination of the osmotic pressure (freezing 

 point method) with little or no laking. If, however, the blood 

 was suddenly cooled to below the freezing point of water, was kept 

 at that temperature for a long time, or was rapidly thawed, pro- 

 nounced haemolysis was produced. Burton-Opitz prepared com- 

 pletely laked blood by eight times freezing it solid, and thawing 

 it rapidly. The mechanism of this laking is not clearly under- 

 stood. Possibly the withdrawal of water from the membrane to 

 form ice might be adduced as sufficient reason (Guthrie). (Cf. 

 Test for frozen meat.) 



Endosmotic laking. 



Normally, the corpuscle has within it a concentration of colloids 

 and of crystalloids isotonic with 0-9 per cent, sodium chloride. 

 A similar state prevails, as we have seen, in the plasma in which 

 the corpuscle is immersed. The corpuscular membrane is almost 

 semipermeable. That is, water may pass through it but not 

 certain salts in solution and not colloids. If the concentration of 

 salts and colloids inside and out of the membrane were not exactly 

 balanced, water would pass from the place of low concentration 

 to that of high concentration (see Osmotic pressure, Chap. V.). 

 That means that blood dropped into water or into a solution of 

 lower concentration than 0-9 NaCl would gain water. Water 

 would pass into the corpuscle, cause it to swell, and when the limit 

 of elasticity had been passed, the corpuscle would burst and 

 scatter its contents into the fluid. 



Crenation. 



Loss of water by evaporation or by immersion in a solution more 

 concentrated than 0-9 per cent. NaCl causes the corpuscles to 

 shrink and shrivel. They then break up into fragments, due to 

 inequalities in the tensile strength of the corpuscle. Most peculiarly 

 the first stage in exosmotic laking is a swelling of the corpuscle. 

 Some change in the physico-chemical state of the protein moiety 

 in the envelope is indicated. It has been shown that the power 

 of colloids to imbibe water may be altered by alterations in their 

 crystalloid content. 



