HAEMOLYSIS AND IMMUNITY 



Haemolysis. If small amounts of blood be taken in two test- 

 tubes and diluted with physiological saline (0-8 per cent. NaCl 

 solution) and with distilled water respectively, it will be seen that 

 there is a marked difference between the red fluid contained in 

 the two tubes. The blood diluted with physiological saline is red 

 and opaque; that distilled with distilled water is red and clear. The 

 blood has become " laked," or haemolyzed, by the water. By means 

 of the change to a clear red solution it is easy to say when haemolysis 

 has taken place. Very slight traces of haemolysis may be detected 

 in the upper layers of the tube when the corpuscles have sunk to the 

 bottom. By haemolysis is understood the process in which a red 

 corpuscle is damaged so that the haemoglobin contained within 

 passes into the surrounding fluid. Haemolysis or laking is always 

 due to injury of the stroma or envelope of the red corpuscle, and may 

 be induced by a number of means: 



(a) Physical. 

 (6) Chemical. 



(c) Foreign sera. 



(d) Bacterial toxins. 



(e) Vegetable poisons. 



(/) Animal poisons such as snake venoms. 



Physical. The addition of physiological saline to blood does not 

 cause laking because it contains salt (NaCl) in about the same concen- 

 tration as that of the salts in the plasma. There is therefore no great 

 interchange of water between the added fluid and the red corpuscles. 

 The addition of distilled water causes laking because it contains rib 

 salts in solution. The red corpuscles of the blood contain inorganic 

 salts in the ionized state. When the distilled water is added to the 

 blood, water passes into the red corpuscles, until there is produced 

 an equal concentration of ions on either side of the corpuscular en- 

 velope. The water passing in greatly distends the corpuscle and 

 eventually ruptures the envelope. The pigment contained in the 

 corpuscle then passes into the surrounding medium, and, becoming 

 dissolved in it, forms the clear red solution characteristic of haemolysis. 

 The membrane of the corpuscle forms a semi-permeable membrane 

 which is easily permeated by the water but does not allow the salts 

 to pass out. Alternate freezing and thawing also damage the envelope 



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