CHEN AT ION 319 



inipernioablc to colloids and to most crystalloids. This has 

 Ijccii determined by estimating the electrical conductivity 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 formalin, which prevents 

 the egress of the pigment but not of the salts. 



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

 lack of 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 understood. 

 Possibly the withdrawal of water from the membrane to form 

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

 frozen meat.) 



Endosmotie 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. Y.). 

 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 



