196 PUBLIC HEALTH BACTERIOLOGY 



phase tends to accentuate it, while after the increasing or 

 " Positive Phase " has begun, an injection causes it to 

 reach a still higher level. The negative phase is usually 

 completed in twenty-four hours, and the positive in three 

 to four days. Wright recommends that the succeeding 

 injection should be given when the positive phase has just 

 reached its summit. In tuberculosis, Koch's bacillary 

 emulsion is used, and the dose is minute, ^qtj- m g r -> 

 gradually increased to TTr Vr7 m g r - I n vaccination against, 

 and in, enteric fever, a standardized strain of Bacillus 

 typhosus is used. 



Leucocyte Extract. The action of the leucocytes in 

 phagocytosis, and of the alexines, which some believe to 

 be derived from them, led Hiss to experiment with leuco- 

 cytic extracts. These were obtained by the intrapleural 

 injection of aleuronat, which produced a copious cellular 

 exudate in 24 hours. The animal being used (a rabbit) is 

 killed, and the exudate removed, with every precaution to 

 ensure avoidance of contamination, and the cells are 

 obtained by centrifugalization. The deposited cells are 

 treated with sterile distilled water, and thoroughly beaten 

 with a platinum spatula. Smears are made, stained by 

 Jenner's method, and examined for bacterial contamination ; 

 cultures are made to detect the same ; more sterile water 

 is added, and the steps are repeated after incubating for 

 8 hours. If no bacteria are found, the resulting fluid is put 

 into the refrigerator until used. Such extracts of exudate 

 cells, on intraperitoneal or subcutaneous injection, have 

 markedly modified the course of infections in the rabbit 

 and guinea-pig, prolonging life, and in some cases prevent- 

 ing a fatal issue from an otherwise lethal dose. Beneficial 

 effects have been observed in man in lobar pneumonia, 

 erysipelas, and in staphylococcal infections. The action 

 of the extract on the bacterial products or toxins seems 

 to be a neutralizing or destroying one. The substances 

 present in these extracts have been called " endolysins," 

 and are different from the serum bacteriolysins, (1) in 

 not being inactivated under 8o C. ; (2) when heated 

 above 8o C. they are destroyed, and cannot be reactivated 

 by the addition either of fresh serum or of unheated 

 leucocyte extract. They are not increased by immuniza- 



