THE CIRCULATING LIQUIDS OF THE BODY 29 



presently the blood-pigment has left the corpuscles, we are apt on 

 first impulse to attribute the whole effect to the foreign material 

 added. We are apt to say that the saponin, the ether, the alien 

 serum, has laked the blood. In a certain sense this is true, but it 

 is not the whole truth. In reality the haemolytic agent has acted 

 in an essential degree, although not exclusively, by overthrowing 

 the equilibrium between the corpuscles and the aqueous solution of 

 certain substances in which they are suspended. To say that the 

 foreign substance alone causes the haemolysis is no more accurate 

 than it would be to say that a man swimming strongly in a rough 

 sea, who sinks when hit and stunned by a piece of wreckage, was 

 drowned by the blow, and not by the sea. No doubt it is true that, 

 but for the blow, he would have continued to swim ; yet, in reality, 

 he loses his life because he is environed by a medium deadly to him 

 as soon as his power of adjustment to it has been too much diminished. 

 On land, the blow would have stunned, but would not have killed 

 him. In like manner, to glance at one phase of the natural decay 

 of the corpuscles within the body, an erythrocyte may float secure 

 in its watery environment through many rounds of the circulation. 

 But its security is not static, like that of a log floating on the water. 

 It is dynamic, a triumph of perfect physico-chemical poise, as the 

 security of the swimmer, still more of the tight-rope dancer, is 

 dynamic, a triumph of perfect neuromuscular poise. The time, 

 however, arrives when, either through changes in the corpuscle 

 itself (the changes of cellular senility, as we may call them), or 

 through changes in the environing medium, or through a combina- 

 tion of the two, the adjustment is upset, and the erythrocyte is now 

 destroyed by the plasma in which it has so long lived. 



In general haemolysis by foreign serum is preceded by agglu- 

 tination or aggregation of the corpuscles into groups. Agglutina- 

 tion may be obtained without haemolysis by heating the haemo- 

 lytic serum to the temperature at which the complement is 

 destroyed, since the agglutinating agents, or agglutinins, are 

 relatively resistant to heat. When the corpuscles of one animal 

 are injected intraperitoneally or subcutaneously into an animal 

 of a different kind, the serum of the latter acquires the property 

 of agglutinating and laking the corpuscles of an animal of the 

 same kind as that whose corpuscles have been injected. This is 

 especially marked if the injection is several times repeated at 

 intervals of a few days. If, for instance, dog's corpuscles are 

 injected into a rabbit, the rabbit's serum after a time becomes 

 strongly haemolytic for dog's corpuscles. It also agglutinates 

 them. This is due to the appearance in the rabbit's serum of 

 an amboceptor and an agglutinin which have a specific action on 

 dog's corpuscles. Many other cells besides the coloured blood- 

 corpuscles give rise, when injected, to similar specific substances 

 (cy tolysins) , which cause destruction of cells of the same kind 

 e.g., leucocytes and spermatozoa. The process of haemolysis is 

 more easily followed than the cytolysis of ordinary cells. Yet 

 in its main features it is essentially similar. Hence it has been 

 studied not only for its own interest, but even more for the light 



