THE HEMOLYTIC REACTION 313 



fatalities so often attendant upon the earlier practices of 

 transfusion, when it was customary, after a severe hemor- 

 rhage, in certain cases of poisoning, especially by carbon 

 monoxide, and in certain pathological states, to transfuse 

 the blood of animals into the veins of man for purposes of 

 resuscitation. So convinced was Landois of the danger at- 

 tendant upon the practice that he states : the blood of animals 

 should never be transfused into the bloodvessels of man. 

 For a somewhat shorter time we have known that if such 

 toxic alien blood be injected into animals in non-fatal quan- 

 tities, that repeated injections of gradually increasing doses 

 may be made until a condition develops in which the 

 receptive animal is immune from the poisonous action of 

 the alien blood. When this point is reached the blood of 

 the immunized animal exhibits specific reactions with the 

 alien blood that are not only of very great theoretical interest, 

 but, as newer developments demonstrate, are susceptible 

 of application to the solution of other problems relating to 

 infection and resistance. Thus, for instance, if a portion of 

 the same blood used in immunizing the animal be repeatedly 

 washed in physiological salt solution until one has nothing 

 left but red-blood corpuscles suspended in salt solution 

 and to this there be added a small amount of the blood, 

 serum from the immune animal, and the mixture be allowed 

 to stand for a little while at body temperature, there will 

 be a more or less complete solution of hemoglobin from the 

 washed corpuscles and their stroma will finally collect at the 

 bottom of the vessel as a more or less pale or colorless mass. 

 If instead of using in the experiment the serum just as it 

 comes from the immune animal, we heat it for thirty minutes 

 to 55 C., and then mix it with the same volume of washed 

 corpuscles suspended in salt solution, we find that no solution 



