CELLULAR RESISTANCE 169 



ticularly from glycerol extracts and the desiccated precipitate may be 

 preserved almost indefinitely. In the moist state temperatures of from 

 50 to 65 C. increase its activity, but at 70 to 75 C. it is destroyed. 

 It acts best in weakly alkaline or neutral medium, and is inhibited by 

 acid. It differs from trypsin in that it is much less active; it does not 

 require activation by any such substance as enterokinase, and exists 

 within the cells in an active state rather than in the form of zymogen. 

 It differs from the bactericidal extracts in that it cannot kill bacteria, 

 but may digest them after their death. The blood possesses an anti- 

 enzyme, but when the cells accumulate in bulk, as in the case of inflam- 

 matory exudates, the anti-enzyme is overbalanced and the protease 

 dissolves necrotic cells, dead bacteria and other detritus. It is of 

 considerable importance in the resolution of lobar pneumonia. In 

 addition the leucocytes are stated to contain amylase, diastase, catalase, 

 oxidase, peroxidase, nuclease and an ereptic ferment, but there appears 

 to be a difference of opinion in regard to lipase. 



Opie has described an additional ferment in areas rich in large 

 mononuclear cells, which acts best in a very weak acid medium. It is 

 inhibited by temperatures of 50 to 65 C., by alkali and by the con- 

 centration of HC1 (0.2 per cent.) favorable for the action of pepsin. 

 He was able to demonstrate this ferment in hyperplastic lymph-nodes 

 rich in large mononuclear phagocytes. It is closely related to the 

 enzymes of tissue autolysis. The acid medium which favors the action 

 of this enzyme inhibits the activity of anti-enzyme. 



Leucocyte Extracts for Therapeutic Purposes. Petterson noted 

 that when leucocytes are placed in contact with blood serum for several 

 hours the mixture is more actively bactericidal than the serum alone 

 or salt solution extracts of the leucocytes. This led to experiments in 

 which he injected leucocytes simultaneously with anthrax bacilli into 

 dogs and found a moderate protection by this treatment. Opie similarly 

 observed that the injection of leucocytes and tubercle bacilli into the 

 pleura of dogs led to less severe manifestations than when tubercle 

 bacilli alone are injected. Probably the most important contributions 

 to the treatment of disease by leucocyte extracts are the studies of Hiss 

 with the collaboration of Zinsser, Dwyer and others. Hiss obtained the 

 leucocytes from pleural exudates produced by the injection of aleuronat 

 suspensions. This was centrifuged before clotting occurred and the 

 cells emulsified in distilled water. Either the leucocytes or the leu- 

 cocytes and supernatant fluid were employed for treatment. From 

 experiments with staphylococcus, pneumococcus, streptococcus, meningo- 

 coccus and typhoid bacillus infections in rabbits, it was determined that 

 protection was afforded by the extracts and that the infection was 

 favorably influenced if therapeutic doses were given as late as twenty- 

 four hours after infection. Encouraging results were also obtained in 

 the treatment of human cases of pneumonia, meningitis, staphylococcus 

 infections, erysipelas and other diseases. In analyzing the beneficial 

 effects of this form of treatment, it was found that the bactericidal 

 properties of the extracts are not sufficiently great to explain their 



