122 Immunity 



"complement" of "addiment" of Ehrlich is also called alexin and 

 cytase. Ehrlich conceives every amboceptor and every comple- 

 ment to be specific, but Bordet and others, while admitting that 

 the amboceptor is specific, hold that there is but one complement 

 or cytase. 



It has already been said that Metchnikoff's primitive con- 

 ception of the body being defended against infection through the 

 phagocytic incorporation and digestion of the microparasites, has 

 had to be modified to conform to the increasing information upon 

 the immunity reactions. He has persistently clung to the idea 

 that the phagocytes are the essential factors, but has changed the con- 

 ception of "phagocytosis" to make it applicable to the new require- 

 ments. He now teaches that when invasive micro-organisms enter 

 the body, chemotactic influences determine that they shall be met 

 by phagocytes. If the invading micro-organisms are too powerful 

 and the phagocytes are kiUed, phagolysis or dissolution of the phago- 

 cytes liberates their enzymes into the blood. These liberated 

 enzymes still act deleteriously upon the invaders, tending to ag- 

 glutinate^ — aggregate them in clumps^ — and sensitize them to the 

 future action of other phagocytes by which they may be taken 

 up. Through extensive phagolysis, and the liberation of large 

 quantities of the enzyme contents of the phagocytes into the blood, 

 the plasma and serum acquire a "fixing" of "sensitizing" quality 

 from the macrocytase of the macrophages, which is the "fixateur" - 

 or "substance sensibilisatrice," and a bacteria-dissolving quality 

 forms another enzyme, microcytase, from the microphages. Thus, 

 we find that Metchnikoff is prepared to account for the "ambo- 

 ceptor" or "immune body" of Ehrlich, which is the macrocytase, 

 and the "complement," which is the "microcytase." In cases 

 where the bacteria exert a negatively chemotactic influence upon 

 the leukocytes, no immunity exists. 



The antitoxins are similarly accounted for by Metchnikoff: the 

 cellular digestive enzymes exert their action not only upon the 

 microparasites, but also upon their products, fixing or otherwise 

 altering them until they can be finally destroyed. 



It will thus be seen that the two chief theories of immunity, though 

 they appear discordant when explained independently of one 

 another, can be fairly well harmonized. Ehrlich believes the im- 

 mune bodies to be the products of those cells of the body with whose 

 haptophile combining groups the haptophore groups of the antigen 

 engaged, and does not attribute the function to any particular 

 group of cells; Metchnikoff attributes all the activities to the 

 phagocytes, and especially the leukocytes. Ehrlich looks upon the 

 phenomena as chemical and pictures them as taking places inde- 

 pendently of the cells; Metchnikoff looks upon them as vital and 

 brought about by the agency of Kving cells. Both theories are 

 ultimately chemical. 



