1011] on Physical Chemistry and the Doctrine of Tmmnnity. 221 



In many cases lecithin has a very strong action. If red blood- 

 corpuscles have been in contact for half an hour with an isotonic 

 salt-solution containing only about ?> per cent, of an emulsion with 

 • 1 per cent, lecithin, they are hemolysed to the same degree by a 

 certain quantity of an acid, as by the threefold quantity of the same 

 acid, if they have not been treated with lecithin. Probably this 

 action of the lecithin is connected with the double action, one 

 coagulating, and one hemolytic, of the acids. When the coagulation 

 has reached a certain stage it hinders the hemolysis. On the other 

 hand, treatment with lecithin seems to hold back the coagulation. 

 This gives the explanation of its favourable influence on the hemolytic 

 action of acids. The hemolytic action of bases, which do not coagu- 

 late the red blood,-corpuscles, is not increased by means of lecithin. 

 Mercuric chloride which possesses also a strong coagulating action 

 acts more strongly hemolytic on blood-corpuscles if they have been 

 treated with lecithin than on common blood-corpuscles. Lecithin has 

 an extremely great influence on the hemolytic action of cobra-poison. 

 It was believed for a long time that this action was due to the forma- 

 tion of a very strongly hemolytic compound of cobra-poison and 

 lecithin, called cobra-lecithid. Through quantitative experiments I 

 showed that neither the cobra-poison nor the lecitliin is consumed on 

 the formation of the hypothetical compound, whereby its existence was 

 made very doubtful. Later investigations seem also to indicate that 

 this compound does not exist. The action of lecithin is tlierefore 

 that of a " sensibilisator " in this case, a theory first enunciated by 

 Bordet in 1898. 



There is a case in which lecithin exerts an opposite influence, 

 namely, the hemolysis by means of saponin. Substances which 

 dissolve fats, for instance, alcohols and ether, exert also a weak 

 diminishing influence on the hemolytic action of saponin, but a 

 weak increasing influence on the hemolysis of red blood-corpuscles, 

 treated with lecitliin, by means of cobra-poison. 



VIII. — Neutralization of Toxins by ^ieans of Antitoxins, 



We now come back to the central problem in immuno-chemistry, 

 namely, that regarding the action of antitoxins on toxins. It has, as 

 stated above, been found by Ehrlich that if a certain addition <tf diph- 

 theria antitoxin neutralizes nO per cent, of a given diphtheria poison, 

 then the double quantity is not able to completely neutralize the poison, 

 and even an addition of the three- or four-fold quantity does not 

 make the poison innocuous. This behaviour agrees wholly with the 

 phenomena observed on neutralization of a weak acid, such as boric 

 acid, with a weak base, such as ammonia. This is seen by a com- 

 parison of the two following tables, of which the one relates to the 

 neutralization of tetanolysin by means of its antilysin, the other gives 



