RELATION OF TOXINES TO ANTITOXINES. 51 



bination is so weak that the numbers obtained do not need 

 correction. 



This explains why a lower limit is found in which hcemolysis is 

 entirely absent with ammonia and sodium hydroxide, but not with 

 tetanolysine. 



Series of experiments were next instituted, in which variations 

 were made in the percentage of blood-corpuscles on the one hand, 

 and the amount of " toxine " (using the word in the above-men- 

 tioned sense) on the other hand. The simplest case is that 

 in which the toxine is present in such excess that complete 

 haemolysis immediately ensues. If, in this case, we plot a curve, 

 and place percentage amounts of the blood on the abscissae, and 

 the degrees of haemolysis on the ordinates, the latter will natur- 

 ally rise in a continuous line. But if the amount of toxine is 

 smaller, only the initial part of the curve is a straight line 

 i.e., so long as the quantity of blood is still so small that the 

 haemolysis is complete. 



But when the concentration of the blood rises still further, 

 there occurs after a short rise a point where the whole of the 

 " toxine " (ammonia later than sodium hydroxide) has entered 

 into combination, and the curve falls again. The shape of this 

 maximum is sometimes a sharp point and sometimes a horizontal 

 line, according to the difference in the stability of the compounds 

 with the blood-corpuscles. These details of the action of different 

 inorganic simple " toxines " do not concern us here. 



It is, however, extremely important that this maximum is 

 almost entirely absent in the case of tetanolysine at least it 

 cannot be identified with certainty. On the other hand, even 

 this faintly indicated maximum occurs with a much smaller con- 

 centration of the blood than in the case of ammonia, &c. From 

 this it follows that the combination of tetanolysine with the blood- 

 corpuscles is much weaker than in the case of inorganic agents, 

 but that, on the other hand, it takes place so slowly that part of 

 the substance that may subsequently be fixed still shows activity, 

 whereas the combinations with ammonia, &c., take place so 

 rapidly that only the actual excess of " toxine " takes part in the 

 action. 



The proof of the fact that tetanolysine possesses so weak an 

 affinity for the receptors of the erythrocytes might be employed 

 as an argument against the general theory of specific combination. 



We shall return to this question of weak combination in dis- 

 cussing the behaviour of tetanolysine towards antitetanolysine. 



Speed of Reaction of Haemolysis. The measurement of the 

 velocity of reaction is one of the most important means of 



