216 GERMICIDAL SERA 



content of the medium, while the extracellular substance is inactivated 

 by the removal of salt from the serum by dialysis. Daubler came to 

 the conclusion that the germicidal constituent of the serum and that of 

 the leukocytes are not identical, the latter remaining active after being 

 heated to 60 C. He also found that the germicidal substances 

 obtained from the leukocytes of different species differ in measurable 

 degree when tested on the same bacteria. Many other investigators 

 produced evidence of the fact that the intracellular and extracellular 

 germicidal constituents are not identical. 



Petterson designates the intracellular bactericidal constituents of 

 leukocytes and other cells as "endolysis" and his pupil, Kling, sum- 

 marizes our knowledge on this subject as follows: 1. The germicidal 

 substances (endolysins) of the polynuclear leukocytes may be obtained 

 by the following methods (a) By digesting the cells for half an hour 

 at 50 C. in bouillon; (b) by extracting the cells with weak acid or 

 alkali; (c) by alternate freezing and thawing of the cells. They 

 cannot be obtained by digesting with bouillon at 37 C., nor with salt 

 solution, nor with 5 per cent, inactivated serum. 2. As tested on 

 Bacillus subtilis, the endolysin bears a temperature of 65 C. without 

 recognizable effect on its germicidal action, and it is not until the 

 temperature is increased to 75 C. that any such effect is noticed. The 

 endolysins can in daylight at room temperature, and in the dark at 37 

 C.,- be evaporated to dryness, and in this state they may be heated for 

 half an hour at 100 C. without being destroyed. The serum germi- 

 cides may be obtained in the dry state in the same manner, but when 

 heated to this temperature they are inactivated. The endolysis, as 

 tested on the subtilis, does not pass through a Pukall filter, while the 

 serum germicide does. The endolysins, as tested on the subtilis, the 

 anthrax and the typhoid bacillus are destroyed by the Roentgen ray, 

 while the serum germicide is not. The endolysins can be extracted 

 with ether, while the serum lysins are destroyed by ether. 3. The 

 activity of an inactivated extract of the leukocytes of the rabbit, as 

 tested on the subtilis, may be restored by the addition of a small 

 quantity of the serum extract in a fresh state. Likewise, an inacti- 

 vated normal serum of the rabbit or the inactive serum of the guinea- 

 pig may be complemented by the addition of a small amount of the 

 leukocytic extract from the rabbit or guinea-pig, respectively. Fur- 



