346 INFECTION AND IMMUNITY 



emulsion is thoroughly beaten up with a stiff bent platinum spatula. 

 Smears are now made on slides, stained by Jenner's blood stain, 

 and examined for possible bacterial contamination. It is well also 

 to take cultures. Sterile distilled water is then added to each tube, 

 about twenty volumes to one volume of sediment, and the tubes are 

 set away in the incubator for eight hours. At the end of this time 

 the sterility is again controlled as above, and further extraction in 

 the refrigerator continued until the extract is used. 



Experiments by Hiss and by Hiss and Zinsser showed that leu- 

 cocytic extracts injected into animals infected with various or- 

 ganisms exerted a distinct though not very powerful therapeutic 

 effect. They have also had a certain degree of beneficial effect in 

 human beings suffering from various infections. However, it is our 

 present opinion, based chiefly upon the researches of one of us with 

 Tsen, 24 that the leucocytic substances act in more or less the same 

 way as do other non-specific proteins, in that they produce an 

 increased leucocytosis and perhaps, as pointed out by Jobling and 

 Petersen in another connection, may lead to an increased discharge 

 of the blood of various proteolytic and other enzymes. 



That bactericidal substances can be extracted from leucocytes 

 by various methods has been repeatedly shown by Schattenfroh, 

 Pettersen, Korschun, and others. 25 The researches of Pettersen as 

 well as, more recently, the work of Zinsser, have shown that these 

 "endolysins, " as Petterson has called them, have a structure quite 

 different from that of the serum bacteriolysins in that they are not 

 rendered inactive by temperatures under 80 C., but, when once 

 destroyed by higher temperatures, can not be reactivated either by 

 the addition of fresh serum or of unheated leucocyte extracts. The 

 last-named authors, moreover, have shown that these endocellular 

 bactericidal substances are not increased by immunization, the quan- 

 tity present in each leucocyte being probably at all times simply 

 sufficient for the digestion of the limited number of bacteria which 

 can be taken up by the individual leucocyte. 



23 Hiss, Jour. Med. Kes., N. S., xiv, 3, 1908. 



24 Zinsser and Tsen, Jour, of Immun., 2, 191 7. 



25 SchattciifroU, Arch. f. Hyg., 1897; Pettcrxon, Cent. f. P>akt v I, xxxix, 1905- 

 and ibid., xlvi, 1908; Korschum, Ann. de 1'Inst. Pasteur, xxii, 1908; Zinsser, 

 Jour. Med. lies., xxii, 3, 1910. 



