28 A MANUAL OF PHYSIOLOGY 



incapable of acting, even in the presence of amboceptor, if the 

 temperature is reduced to o C. Nevertheless the corpuscles 

 take up amboceptor at this temperature, and on this fact is 

 based a method of freeing serum from amboceptor. For ex- 

 ample, if dog's serum and excess of rabbit's washed corpuscles, 

 both previously cooled to o C., be mixed and placed at o C. for 

 some hours, and the serum then removed, it will be found that it 

 has lost the power of laking rabbit's corpuscles, washed or un- 

 washed, at air or body temperature, although it will still do so 

 on the addition of dog's serum in which the complement has been 

 destroyed by heating it to 56 C. 



As to the manner in which haemolytic agents cause the liberation 

 of the blood-pigment, the fact that in so many forms of laking the 

 corpuscles swell up before the haemoglobin escapes indicates that 

 the entrance of water is an important step. The entrance of water 

 is favoured by changes produced in the chemical and physical con- 

 dition of certain constituents of the superficial layer (envelope) of 

 the corpuscle, as well as by changes in its interior. Saponin and 

 ether, for example, are known to be solvents of cholesterin and 

 lecithin, and cholesterin and lecithin are important constituents of 

 the stroma and envelope of the erythrocyte. It is easy to under- 

 stand that if a portion of one or both of these substances is dis- 

 solved, or altered without being actually dissolved, profound changes 

 may be produced in the permeability of the corpuscle to water and 

 to the salts dissolved in the liquid in which the erythrocytes are 

 suspended. In addition to this change of permeability, many laking 

 agents, perhaps all, exert also a more direct influence on the normal 

 relations of the native blood-pigment to the stroma. Ether and 

 saponin, for instance, seem to act in two ways by disorganizing 

 the envelope through solution of its lipoids, and thus increasing its 

 permeability to water ; and by helping to dissociate the blood - 

 pigment-stroma complex by exerting a pull on the lipoids of the 

 stroma, while the water simultaneously exerts a pull on the pigment. 



The conclusion follows from this view of haemolysis that the 

 erythrocytes, normally so perfectly adapted to the plasma in which 

 they float, may, when the conditions on which their equilibrium 

 with it depends 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 



