524 INFECTION AND RESISTANCE 



fats, and carbohydrates. That such processes also go on in the living 

 body is probable, although, as we have stated in an earlier chapter, 

 it is a well-known fact that living cells oppose a more or less mysteri- 

 ous resistance to enzymic digestion, just as they oppose a similar 

 resistance to bacterial invasion. The phenomenon is more fully 

 discussed by Wells in his "Chemical Pathology," to which the reader 

 is referred. It is not improbable that this resistance to invasion and 

 enzyme attacks, spoken of vaguely as "vital resistance," can be anal- 

 yzed into more exact factors, one of which seems to be the question 

 of reaction, digestion depending to some ex:ent upon the reduction 

 of alkalinity by the formation of acid in the tissue cells. 



However, the physiological importance of tissue enzymes is a 

 subject which we cannot go into in this connection, since the rela- 

 tionship of these enzymes to normal body metabolism is a subject 

 more fully dealt with in text books of physiology and is too far 

 removed from the subject of our present discussion to warrant ex- 

 tensive analysis. It must, of course, be self-evident that the existence 

 of cellular ferments of this nature must play an important role 

 wherever and whenever cell death occurs, and since such cell death 

 is an accompaniment of many phases of bacterial infection it may 

 well be that the enzymes which destroy dead cells, whether they be 

 bacterial or those of the body itself, contribute to the general patho- 

 logical picture characterizing such diseases. Moreover, the impor- 

 tance of the enzymes is particularly enhanced by the knowledge we 

 have gained from the work of Vaughan and others, who have shown 

 that in the course of proteolytic cleavage toxic substances are lib- 

 erated. It is such proteolysis which is the probable basis of the 

 formation of the "anaphylatoxin" of Friedberger, the "proteotoxin" 

 about which we ourselves have written, and the "sereotoxin" of 

 J obling and Petersen ; and similar processes are involved in the toxic 

 substances, studied by Whipple, which form in the intestine as a 

 consequence of ligature of the gut. It is conceivable that wherever 

 and whenever a proteolytic ferment reacts in the body with its 

 substrate, toxic cleavage products result, perhaps in the form of 

 albumoses, peptones, etc., which are rapidly absorbed and cause 

 symptoms of varying intensity. In the chapter on anaphylaxis we 

 have seen that many writers have attributed the injury occurring in 

 this phenomenon to the formation of such split products and there is 

 much evidence in favor of such a view, although the rapidity and 

 vehemence of anaphylactic shock indicate that probably there are 

 purely physical elements also involved which we do not as yet com- 

 prehend. 



Of the cells in the body with which enzyme study has been most 

 assiduously followed, the most important are the leucocytes. We 

 have already had much to say in the chapters on phagocytosis of the 

 digestive functions of the white blood cells. However, we dealt with 



