AGGRESSINS 291 



In applying this method of treatment, by subcutaneous injections, 

 to infections in man. Hiss and Zinsser observed distinctly beneficial 

 results in cases of epidemic cerebrospinal meningitis, in lobar pneumonia, 

 in staphylococcus infections, and in erysipelas/ 



In experimenting with the leucocyte extracts in vitro the same au- 

 thors were able to show that precipitates occurred when clear leucocyte 

 extract and the clear extract of various bacteria were mixed. ^ 



Further experiments, carried out both in animals and in the test tube, 

 showed that while the leucocytic extracts possessed slight bactericidal 

 powers for a variety of microorganisms, these attributes did not seem 

 sufficient to explain the profound, modifying influences exerted upon 

 bacterial infections by these extracts. Experiments have also shown 

 that the leucocyte extracts possess some distinct power of neutralizing 

 or destroying the poisonous products of typhoid and dysentery baciUi. 

 Whether or not the final explanation of the action of these extracts will 

 be found to lie in these endotoxin-neutralizing properties of the leuco- 

 cytic substances, can not as yet be determined, and this problem must 

 be left for further research to decide. 



That bactericidal substances can be extracted from leucocytes by 

 various methods has been repeatedly shown by Schattenfroh, Petter- 

 son, Korschun, and others.' The researches of Petterson 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 tem- 

 peratures, 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 endoceUular bactericidal substances are not 

 increased by immunization, the quantity 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. 



AGGRESSINS 



An extremely obscure chapter in our knowledge of the reaction of 

 animals and man against infection is the one dealing with the questions 



' Hiss and Zinsser, Jour. Med. Res., N. S., xiv, 3, 1908; ibid., xv, 3, 1909. 



^ Hiss and Zinsser, ibid., xiv, 3, 1908. 



'Schattenfroh, Arch. f. Hyg., 1897; Petterson, Cent, f . Bakt.,I, xxxix, 1905, and 

 ibid., xlvi, 1908; Korschun, Ann. de I'inst. Pasteur, xxii, 1908; Zinsser, Jout. Med. 

 Res., xxii, 3, 1910. 



