FURTHER DEVELOPMENT OF KNOWLEDGE 169 



alexin, Metchnikoff and his school have nevertheless adhered to this 

 conception for various additional reasons. 



Metchnikoff distinguishes between two kinds of alexin the 

 microcytase, which is the bactericidal complement or alexin, and 

 is supposed to originate from the microphages or polynuclear leu- 

 kocytes, and the macrocytase, which represents the hemolytic and 

 cytolytic alexin or complement, and originates from the mononuclear 

 cells or macrophages. As in the case of the bactericidal alexin, ex- 

 traction methods have been employed to demonstrate that the hemo- 

 lytic alexin took its origin in the macrophages, and at Metchnikoff' s 

 suggestion, Tarassewitch 5 prepared hemolytic substances by extract- 

 ing spleen tissue and other a macrophagic organs" in various ways. 

 Here again the identity of the hemolytic extracts with serum hemoly- 

 sins has been placed in doubt. Korschun and Morgenroth 6 have 

 shown that the hemolytic organ extracts were heat stable and alcohol 

 soluble ; Donath and Landsteiner, 7 and others, have obtained similar 

 results. It would be quite thankless to review the extensive literature 

 which has accumulated upon this point. It would seem, in summariz- 

 ing it, that no definite proof of the presence of true, active alexin, 

 either hemolytic or bactericidal, within the leukocyte or mononuclear 

 cells has been brought by methods of extraction, and the apparently 

 positive results reported by earlier observers are adequately explained 

 by the discovery of the heat-stable and non-reactivable bactericidal 

 and hemolytic substances in extracts of such cells by Schattenfroh, 

 Korschun and Morgenroth, and many others. It appears, moreover, 

 from these investigations that probably the intracellular substances 

 by which the digestion of ingested bacteria or blood cells is brought 

 about are of a nature entirely distinct from that of the serum anti- 

 bodies and alexins. A very ingenious demonstration of this is found 

 in an experiment first made by RTeufeld. Neufeld 8 allowed leu- 

 kocytes to take up highly sensitized red cells. Instead of undergoing 

 prompt hemolysis, as they would if small amounts of alexin had been 

 added, they were slowly broken up without hemolysis, fragments of 

 hemoglobin remaining after complete morphological disintegration 

 of the erythrocytes. At no time were intraphagocytic "shadow'* 

 forms observed. 



The failure to extract alexins from dead leukocytes does not, 

 however, preclude the possibility of the secretion of alexins by living 

 leukocytes. This point is one which is, of course, much more diffi- 

 cult to investigate directly. Indirectly the increased bactericidal 

 properties of exudates rich in leukocytes, as found by Denys and 

 Havet, would point in this direction. However, even this is not 



5 Tarassewitch. Cited from Metchnikoff. 



6 Korschun and Morgenroth. Berl kl Woch., No. 37, 1902. 



7 Donath and Landsteiner. Wien. kl. Rundschau, Vol. 40, 1902. 



8 Neufeld. Arb. a. d. kais. Gesundlieitsamt., Vol. 28, 1908, p. 125. 



