30 THE CIRCULATING LIQUIDS OF THE BODY 



are altered, be rapidly and inevitably destroyed by that very plasma 

 itself. It is, indeed, the very fact of the exquisite adaptation of liquid 

 and cell for a strictly regulated exchange of material which constitutes 

 the danger when the regulation is upset. A liquid like mercury, which 

 is not adapted either to give anything to erythrocytes in contact with 

 it or to take anything from them, would not cause haemolysis, even if 

 the permeability of the corpuscles for water or sodium chloride were 

 increased to any extent. The continued survival of the erythrocytes in 

 an aqueous solution of salts and proteins like the plasma nay, more, 

 the protection of the corpuscles up to a certain point by the plasma 

 against the attack of extraneous haemolytic agents are facts we are 

 prone to take so much for granted as to forget that they depend entirely 

 upon a most delicate adjustment of the permeability of the corpuscles 

 for essential constituents of the plasma. Disturb these relations to a 

 sufficient degree, and the plasma becomes a poison to the erythrocytes 

 not much less deadly than distilled water. 



When we add to blood a haemolytic substance, and see that presently 

 the blood-pigment has left the corpuscles, we are apt to attribute the 

 whole effect to the foreign material added, and 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 nob exclusively, by overthrow- 

 ing 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 neuro- 

 muscular 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 combination 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 agglutina- 

 tion or aggregation of the corpuscles into groups. Agglutination 

 may be obtained without haemolysis by heating the haemolytic 

 serum to the temperature at which the complement is destroyed, 

 since the agglutinating agents, or agglutinins, are relatively resistant 

 to heat. Besides the amboceptors naturally present in the blood 

 of certain animals, and capable, in conjunction with complement, of 

 haemolyzing the corpuscles of certain other animals, amboceptors 

 may be produced in much greater strength by artificial means. 



