438* H^EMOLYSINS AND ALLIED BODIES 



had been destroyed. The inactivated serum could be reactivated, 

 i.e. made again haemolytic towards rabbit's erythrocytes, by mixing 

 it with some normal (guinea-pig's) serum. To make this clear, we 

 will take an actual experiment. A guinea-pig receives several 

 peritoneal injections of rabbit's defibrinated blood until its blood 

 serum becomes markedly heemolytic towards rabbit's erythrocytes, 

 i.e. until a fraction of a cubic centimetre can lake 1 c.c. of a 5 per 

 cent, suspension of rabbit's erythrocytes. The haemolytic guinea-pig's 

 serum is then inactivated by placing it for thirty -five minutes in 

 a water-bath at 55 C. After cooling, an excess of the inactivated 

 serum, added to the suspension of rabbit's erythrocytes, produces 

 no laking ; but, if the inactivated serum be mixed with a minute 

 quantity (a fraction of a cubic centimetre) of. a normal guinea-pig's 

 serum, the mixture very quickly hsemolyses. The amount of in- 

 activated serum necessary for laking when normal serum is also 

 present is exceedingly small 0- 005-0- 001 c.c. being sufficient for the 

 complete laking of 1 drop of blood. 1 



Two things must therefore be necessary for haemolysis ; one of 

 them present in inactivated serum (can withstand heating), the 

 other in normal serum (is destroyed by heating). It must be the 

 former of these (i.e. the heat-resistant substance) which is pro- 

 duced by injecting the erythrocytes into a different animal. 

 Regarding the other (the unstable body, which is present in 

 normal serum), Nuttall in 1888 had shown normal serum to pos- 

 sess antibacterial properties, and Buchner, later, showed it to be 

 capable of partially destroying foreign erythrocytes as well as 

 bacteria. This latter worker ascribed this power to the presence 

 in the serum of a substance which he called alexin, and this, 

 Bordet considered as the agency in normal serum which reactivated 

 hsemolytic serum, previously inactivated by heat. The substance 

 which inactivated serum contained, and which had evidently been 

 produced by injection (since it was contained only in the serum 

 of injected animals), Bordet thought to be of the nature of a 

 mordant. According to him, this mordant, or substance sensibila- 

 trice, as he named it, acted on the erythrocytes by making them 

 sensitive towards the alexin. Furthermore, the sensitising sub- 

 stance was shown to be specific in its nature, it would sensitise 

 only the erythrocytes of an animal of the same species as that 

 from which the blood for injection had been obtained. On the 

 1 Quoted from Hans Sachs. 



