436 HJ3MOLYSINS AND ALLIED BODIES 



(that is, that they have the same molecular concentration) and 

 the envelope is uninjured, no haemolysis will result. Any 

 such solution is said to be isotonic with the corpuscles. If, 

 however, the osmotic pressure of the surrounding fluid be less 

 than that of the corpuscles (hypisotonic), then the corpuscles will 

 absorb water, and become swollen and pale, and ultimately the 

 envelope will burst and so let loose the haemoglobin. This law 

 of osmotic equilibrium does not, however, hold for all salts or 

 neutral bodies ; thus ammonia salts, in whatever concentration, 

 cause the corpuscles to lake, and the same is true for urea. 



We must distinguish sharply between these two classes of 

 haemolytic agencies : those that poison the envelope but do not 

 alter the osmotic relationship of corpuscles and serum, and those 

 which primarily alter the isotonic condition so that certain mole- 

 cules (water, &c.) diffuse into the corpuscle, causing the latter to 

 distend till it bursts, and so lets loose its haemoglobin. 



Included in the group of toxic haemolysins are a number of 

 peculiar bodies which, under certain conditions, may become 

 developed in the blood serum, or may be present in normal serum, 

 or in various tissues or fluids of animal or of vegetable origin. 

 These, in their general behaviour, are so like antibacterial bodies 

 and cell poisons in general, that it is of great importance they 

 should be thoroughly understood. 



It is to Bordet( 4 ) that we owe the discovery of haemolysins. 

 The blood serum of a guinea-pig added to a 5 per cent, suspension 

 of the erythrocytes x of a rabbit in isotonic salt solution produces 

 no laking. If, however, 3-5 c.c. of defibrinated rabbit's blood be 

 injected several times into the peritoneal cavity of a guniea-pig, a 

 few days elapsing between each injection, the serum of the injected 

 guinea-pig will, when added to a suspension of rabbit's eryth- 

 rocytes, be capable of quickly laking them. A haemolysin, capable 

 of killing the stroma of the rabbit's erythrocytes, and so allowing 

 the haemoglobin to diffuse through it, is thus produced in the 

 guinea-pig's blood. If, instead of rabbit's erythrocytes, the eryth- 

 rocytes of any other animal be mixed with this haemolytic serum, 

 no haemolysis will result, or only a slight amount. The haemolysin 

 is therefore specific in its action. 



1 Hereafter, the term erythrocyte will be used instead of red corpuscle. 



