THE PROTEOLYTIC MECHANISM IN OPERATION 81 



disturbing element in its present location. According to the 

 theory here presented, what happens to it is this : the leucocytes 

 having had to deal with this particular type of protoplasm many 

 times before have already secreted into the blood serum an 

 enzyme (allied to trypsin) that is capable of attacking the pro- 

 tein and accomplishing the early stages of its proteolysis. This 

 process will be facilitated if the molecules of foreign protoplasm 

 chances to be engulfed in the body of a leucocyte. But in any 

 event the leucocytic enzymes will hydrolyze the protein to the 

 peptone stage; conceivably to the stage of polypeptids. 



At this stage the partially hydrolyzed foreign protein is turned 

 over to the red blood corpuscles. To them these particular 

 polypeptids are familiar materials, since they have dealt with 

 their like often enough before, and the particular department of 

 their enzymes-making apparatus that will deal with these specific 

 polypeptids is in good working order; indeed, the enzymic prod- 

 ucts are already in the blood stream. So the further hydrolysis of 

 the intruding matter is rapidly carried forward ; with the result 

 that presently the main bulk of the material has been transformed 

 into amino-acids thus supplying normal material for the uses 

 of the cells that are to build up the specific body proteins. 



We must suppose, however, that there is a small residual mat- 

 ter, of doubtful constitution, which has not been thus hydrolyzed ; 

 for the complete hydrolyzation of a protein through the agency 

 of enzymes has not been accomplished in the laboratory, and we 

 have no reason to suppose that it is accomplished in the body. 

 It requires from two to five hours of digestion in strong hydro- 

 chloric acid to hydrolyze protein completely in vitro; the organ- 

 ism has no enzymes of corresponding power. 



But, according to hypothesis, the residual molecules, whatever 

 their exact nature (uric acid, urea, bilurubin), have been largely 

 or perhaps exclusively developed in the bodies of the red cor- 

 puscles ; with the result that the corpuscles themselves are more 

 or less damaged. The residual molecules, that is to say, are 

 poisonous to protoplasm. The red corpuscle in retaining or ab- 

 sorbing them is thus injuring itself, but protecting the body-cells 

 that would otherwise absorb the poison. 



But whereas such an injury to the body-cells would be highly 

 detrimental to the entire organism, the injury to the red blood 

 corpuscle is not necessarily a matter oj consequence. The cor- 

 puscle bearing its poison is whirled on in the blood stream until 

 it comes to the liver, and there destroyed, its noxious molecules 

 being discharged, with countless others of similar origin, into 

 the bile duct. 



It would be interesting to inquire as to just what is the char- 



