THE PROTEOLYTIC MECHANISM IN OPERATION 105 



is furnished by the large mononuclear leucocyte." Another in- 

 terpretation is possible, as I shall show presently, but the experi- 

 ment justifies the conclusion "that in work of this kind lies a 

 promise of at least partially insulating the anaphylactic enzymes 

 and studying their effects." 



"Anaphylactic enzymes," it will be understood, is the term 

 used by Vaughan to describe the so-called antibodies put out in 

 response to foreign proteins, about which we have all along 

 been speaking. 



This experiment certainly shows that in some cases the leu- 

 cocyte may be the agent of origin, or at least of transfer, of 

 the antibodies directed against poisons. It should be added, how- 

 ever, that the elder Vaughan does not ascribe this function ex- 

 clusively to the leucocytes, for he expressly states in another 

 connection that it is possible that the protective enzymes are 

 formed by different cells according to the "sensitizer" (i.e., the 

 proteid toxin) used a view obviously in harmony with the pro- 

 teomorphic theory, though far too general to be cited as spe- 

 cifically supporting the theory. 



In the original presentation of the Proteomorphic theory it 

 was noted, in pursuance of this aspect of the subject, that 

 Vaughan was then testing his extract of mononuclear leucocytes 

 in the treatment of cancer, and the following comment was 

 made, which has peculiar interest in the light of more recent 

 developments : "Whatever the immediate results of this par- 

 ticular test, there is every reason to hope that the method in- 

 augurated, in which the leucocytes are directly looked to for the 

 production of immunizing enzymes, will be generalized and given 

 an important place in therapeutic procedure in the near future. 

 It is a short step from the clear conception that the leucocytes 

 are the chief agents in the producing of immunizing ferments 

 to the direct utilization of the leucocytes themselves in thera- 

 peutic procedure. 



"That an antidote thus prepared may have marked advantages 

 over an antitoxic serum is clearly suggested in the work of 

 Vaughan just referred to. For he found it impossible to use 

 the serum of a 'sensitized' animal, because, in the first place, 

 repeated injections of the serum caused albuminuria ; and, in 

 the second place, they 'sensitized* to the proteins of the serum. 

 The leucocytic extract also 'sensitizes' to the blood serum, until 

 it is passed through a Berkefeld filter, after which it is innocu- 

 ous. All of which may readily be interpreted in terms of the 

 Proteomorphic theory. 



"Here, then, is at least a strong suggestion of the possibility 

 of producing antibodies directly from the filtered bodies of the 

 leucocytes, and avoiding the danger of serum disease which is 



