18 COLLECTED STUDIES IN IMMUNITY. 



by examining a large number of separate cases would such a favor- 

 able combination be found. As a matter of fact after a rather long 

 search, we succeeded in finding such cases. 



As is well known, dog serum dissolves guinea-pig blood with great 

 energy. If it be heated to 57 C. it loses this power, in accord- 

 ance with the usual rule. However if to the 5% guinea-pig blood 

 mixture some of this inactive dog-serum is added, and also a sufficient 

 quantity of normal guinea-pig serum (about 2 cc. to 5 cc. of the 5% 

 blood mixture), complete solution takes place. This fact can be ex- 

 plained only by assuming that the guinea-pig serum contains a 

 complement which happens to fit the haptophore group of the inter- 

 body derived from the dog, and that it thus reactivates this. In 

 this case the proof is all the more convincing because solution is 

 effected by the addition of serum of the same species from which the 

 blood-cells are derived. This serum should be the best possible 

 preservative for the cells, for it represents their physiological medium. 1 



By means of these experiments we regard it as positively proven 

 that the hsemolytic action exhibited by a serum, normally or in 

 response to immunizing procedures, is due, in the cases examined 

 by us, to the combined action of two substances. 



Now that we had at our command the interbody of the haemolysin 

 solvent for guinea-pig blood, derived from dog serum, as well as a 

 complement which reactivated this, we were ready to proceed to 

 the last of our demonstrations. 



To each of two test-tubes containing 5 cc. 5% guinea-pig blood 

 0.2 cc. inactive dog serum were added, after it had previously been 

 ascertained by experiment that 0.2 cc. dog serum previous to heat- 

 ing were just sufficient completely to dissolve this amount of guinea- 

 pig blood. The mixtures were allowed to remain at 20 for half an 



1 We succeeded also in finding other combinations in which an analogous 

 relation in greater or less degree could be demonstrated. Of these we 

 may mention: 1) guinea-pig blood, inactive calf serum, guinea-pig serum; 

 2) sheep blood, inactive rabbit serum, sheep serum; 3) goat blood, inactive 

 rabbit serum, goat serum; 4) guinea-pig blood, inactive sheep serum, guinea- 

 pig serum. The fact that such an interbody, i.e., one derived from one 

 animal species, finds fitting complements not only in its own serum but 

 also in that of different species, is of considerable importance in the question 

 whether curative sera can be made harmless to man by means of pasteurization. 

 Possibly this would serve to explain why heating of the diphtheria curative 

 serum, introduced by Spronck, has not realized the expectations a priori held 

 out for the procedure. 



