PREFACE AND SUMMARY OF CONTENTS. XV 



under this heading, seems to us to have also acquired a number 

 of elucidative factors. The investigations of Metchnikoff, Ehr- 

 lich, Bordet, Pfeiffer, and others were not only sustained in 

 many particulars, but the solidity of many of their deductions 

 was shown by the fact that the addition of considerable new 

 evidence only served to harmonize their views. Phagocytosis 

 proved to be the preponderating factor of immunizing processes; 

 but the spleno-pancreatic internal secretion, trypsin, to which 

 we have just referred as the organic body which reduced toxic 

 albuminoids to inert cleavage products, was found to be the 

 agency which digested bacteria in the digestive vacuoles of 

 phagocytic leucocytes. Indeed, Metchnikoff had found this 

 body to be a trypsin. 



The multiplicity of antitoxins, cytolysins, and haptophore 

 groups which Ehrlich connected with his side-chain theory no 

 longer seemed necessary in the light of our views, the diversity 

 of effects due to toxins, as in the case of poisons, drugs, etc., 

 being ascribable to sundry factors, and especially to variations 

 in their toxicity. Rid of these confusing elements, Ehrlich's 

 labors appeared to us in a new light. His amboceptor (Bordet's 

 sensitizing substance) proved to be our oxidizing substance, and 

 his complement (Buchner's alexins, Metchnikoff's cytases) be- 

 came our spleno-pancreatic internal secretion: trypsin. But 

 we were led, in addition, to ascribe to an organic body which 

 we have already mentioned, fibrinogen, a preponderating part 

 in the process through which all albuminoid poisons (including 

 toxins) and bacteria are converted into benign products in the 

 blood. Indeed, we found that this process required the simul- 

 taneous co-operation of the three agencies named, trypsin only 

 becoming sufficiently active as a proteolytic agent in the pres- 

 ence of given proportions of oxidizing substance and fibrinogen. 

 Insufficiency of either of these three bodies was found to 

 compromise the issue of the disease in which it occurred. In 

 typhoid fever, for instance, fibrinogen was shown by our in- 

 vestigation to be the missing agency; in diphtheria it was 

 trypsin which was found absent from the blood-stream. In- 

 deed, the dominant active principle of antitoxin proved to be 

 trypsin. 



The white corpuscles of the blood were found to be en- 



