STUDIES ON H^MOLYSINS. 75 



only one-half the amount of blood-cells is first added, sufficient time 

 allowed for these to completely dissolve and the second half of the 

 blood-cells added, it will be found that these are no longer dissolved. 

 It appears, therefore, as though the blood-cells were capable of com- 

 bining with double the amount of immune body necessary for their 

 solution. In order to explain this result Bordet describes the follow- 

 ing staining experiment: If one dissolves methyl violet in water, it 

 is possible, by means of a strip of filter-paper dipped into the solution, 

 to abstract all the coloring-matter from the solution. The strip will 

 assume a color of very definite intensity. If, however, the strip is 

 divided into several smaller strips and these are dipped into the 

 fluid one after the other, the first strip will assume a considerably deeper 

 color, whereas the strips last introduced will be unable to abstract 

 any color from the now colorless fluid. From this Bordet draws 

 the following conclusion: 



"On peut admettre, par comparaison, que les premiers globules 

 introduits dans Fhemotoxine sont deja susceptibles de perdre leur 

 hemoglobine lorsqu'ils ne sont encore que " faiblements teints " par 

 les principes actifs, mais qu'ulterieurement ils peuvent absorber une 

 dose beaucoup plus grande de ces substances, epuiser ainsi le serum 

 et empecher la destruction de nouveaux globules introduits dans la 

 suite." 



Phenomena such as those here described have long manifested 

 themselves in our experiments on the binding of the immune body 

 by the erythrocytes although these experiments were of somewhat 

 different form. But before we proceed to discuss these results and 

 our conclusions, we should like to describe the facts observed by us. 



In order to determine the combining ability of the erythrocytes 

 for an immune body, especially when quantitatively accurate results 

 are desired, it is best to proceed as follows: The immune body 

 (hsemolysin heated to56 C.) is added to the red blood-cells and, after 

 a certain time, the mixture is centrifuged. The clear fluid so obtained 

 is tested for free immune body by adding an excess of complement 

 and allowing this mixture to act on the same quantity of fresh blood- 

 cells. If one proceeds in this manner in a large series of cases, employ- 

 ing varying multiples of the solvent dose of immune body, it is possible 

 to determine accurately the combining power of the cells. The 

 following experiment will very readily make this clear. 



The immune body was present in the serum of a sheep which 

 had been treated with dog blood. When this serum was inactivated 



