526 INFECTION AND RESISTANCE 



"caseous" abscess accompanying typical tuberculous lesions owes its 

 peculiar histological characteristics to the lack of proteolytic 

 enzymes. 



Jochmann 6 and his collaborators have extensively studied leuco- 

 cytic extracts in this regard and, curiously enough, found that the 

 proteolytic enzymes of leucocytes of which we have been speaking 

 can be found only in the cells of man and monkeys and, to a slight 

 degree, in dogs. In these species only, according to Pappenheim, 7 

 do the leucocytes contain true neutrophile granules and it is there- 

 fore a possibility that the neutrophile granules and the enzyme action 

 are related to each other. The leucocytes of rabbits do not ap- 

 parently contain protease, but recently in our laboratory Mrs. Parker 

 and Miss Francke have shown that rabbit leucocytes contain erepsin. 



The proteolytic enzymes of leucocytes curiously enough continue 

 their activity at temperatures as high as 55 C., a fact which makes 

 it possible to investigate their activity at temperatures at which most 

 bacteria will no longer grow and functionate, and this incidentally 

 facilitates sterile experimentation. Their activity is astonishing in 

 that Jochmann found instances where dilution even as high as 500- 

 fold with salt solution did not completely eliminate the proteolytic 

 activity of pus. The simplest method of demonstrating such action 

 is to place pus or washed leucocytes, in droplets, upon the surface of 

 plates of Loeffler's coagulated blood serum, such as that used in the 

 cultivation of diphtheria bacilli. On such plates, small indentations 

 rapidly give evidence of the liquefaction of the coagulated protein. 



Casein also can be used as an indicator of proteolytic digestion, 

 a casein solution being made by dissolving a gram of casein in 100 

 c. c. of N/IO XaOH solution and neutralizing this to litmus with 

 deci-normal HC1. A very curious property of the leucocytic ferment 

 has been described by Jochmann and Ziegler, who reported that pres- 

 ervation in 10 per cent, formalin solution will long preserve the fer- 

 mentative activities of the cells. 



It was formerly supposed that the proteolytic properties of 

 leucocytes were more or less pathological. But we have since learned 

 that these powers are common to leucocytes both in health and in 

 disease. The older idea was due to the fact that the earliest investi- 

 gations of the ferments were made in connection with myelogenous 

 leukemia. Jochmann and Ziegler studied the organs of patients 

 dead of this disease and found that the bone-marrow, spleen, and 

 lymph nodes of such cases had powerful proteolytic properties in 

 contrast to the very weak activities in this regard of normal organs. 

 The proteolytic activity was more or less in direct proportion to the 

 degree of myelogenous infiltration. In lymphatic leukemia no such 



6 Jochmann. For summary of his work and literature see Kolle u. 

 Wassermann, 2nd ed., Vol. II, 2. 



7 Pappenheim. Cited from Wiens, loc. cit. 



