MECHANISM OF PROTEIN HYDROLYSIS AND IMMUNIZATION 79 



If the implications of the theory are clearly grasped, it will 

 be obvious that, according to the present view, there is no funda- 

 mental distinction between the various "complements" and "anti- 

 bodies" thus defined. The word "complement" as commonly 

 used merely serves to define such members of an endless series 

 of ferments as are relatively susceptible to the influence of high 

 temperatures. The line of demarcation thus established has ob- 

 vious practical value ; but we should not be led thereby to imag- 

 ine a duality of action which in all probability does not exist in 

 fact. 



What we term "complement" in any given case is the ferment 

 or combination of ferments regularly developed in quantity by 

 the cell in question to meet the more or less habitual needs inci- 

 dent to the ingestion of proteins of its environment. What we 

 term an "antibody" in any given case is one of a series of fer- 

 ments developed in response to a specific impulse given by an 

 individual type of protein or protein product. The trypsin of 

 the leucocyte would stand at one end of that scale; the anti- 

 toxins of the red corpuscle at the other; but there would be 

 intermediate forms to cover all the field between the two, each 

 enzyme doubtless overlapping more or less with its neighbors. 



That the general ferments or complements should be themola- 

 bile and the antibodies relatively thermostable may conceivably 

 be due to the greater complexity of the former, consistent with 

 their more generalized function. But that there is any radical 

 and fundamental distinction in "the nature of the two types of 

 structures seems theoretically improbable. 



The demonstration or refutation of the validity of this assump- 

 tion, however, is a matter for the chemistry of the future, with 

 its extended knowledge of the nature of enzymes in general. 



