FACTORS DETERMINING PHAGOCYTOSIS 321 



by Neufeld and Kimpau, 44 Neufeld and Topfer, 45 Dean, 46 Hektoen, 47 

 and others. It was shown that when an animal is immunized with 

 any given bacterium or other cellular antigen (blood corpuscles, 

 etc.) opsonic substances specific for the particular antigen appear in 

 considerable quantities, and these are but slightly, if at all, dimin- 

 ished when the serum is heated ; Neuf eld and Hiine 48 found that 

 heating for as long as three-quarters of an hour to 63 C. did not 

 noticeably reduce the activity of the bacteriotropins of immune 

 serum, and that, again, unlike the normal opsonins, prolonged pres- 

 ervation, under sterile conditions, changes them but slowly. 



These facts alone indicate a close similarity between the bac- 

 teriotropins and the other well-known thermostable constituents of 

 immune sera, and the question here again immediately arises whether 

 we are to regard them as identical with any of the other specific 

 antibodies or as distinct substances independent of these. 



It was suggested early in these investigations by Muir and Mar- 

 tin that bacteriotropins might be identified with agglutinins, inas- 

 much as they possessed resistance to heat, were active without ap- 

 parent dependence upon alexin, and could not, at least in the earlier 

 studies, be reactivated by the addition of fresh normal serum when 

 once inactivated. The supposition was that for this reason the bae- 

 teriotropin might have a structure like the hypothetical a haptines 

 of the second order" which Ehrlich attributes to the agglutinins. 

 This supposition has found no experimental support in that ag- 

 glutination and bacteriotropic effects did not run parallel. We our- 

 selves are not ready to admit that such lack of parallelism is proof 

 against their identity. However, since it is very probable that both 

 agglutination and precipitation are merely phenomena of colloidal 

 flocculation effects which follow certain quantitatively adjusted com- 

 binations of antigen and specific antibody, and that it is not at all 

 necessary to assume separate agglutinating or precipitating serum 

 constituents, this problem becomes merely another version of the 

 question of the identity of bacteriotropins and sensitizer or ambo- 

 ceptor. 



Apart from thermostability, further similarity lies in the fact 

 that bacteriotropins are strictly specific and may be specifically ab- 

 sorbed out of immune sera by their respective bacteria. 



Like amboceptor or sensitizer they are specifically increased to a 

 powerful degree by the treatment of animals with any given micro- 

 organism and may be incited not only by the injection of bacteria 



44 Neufeld and Rimpau. Deutsche med. Woch., No. 40, 1904; Zeitschr t 

 f. Hyg., 51, 1905. 



45 Neufeld and Topfer. CentralU. f. Bakt., 1, 38, 1905. 



46 Dean. _Proc. Eoy. Soc. B., 76, 1905. 

 47 -Hektoen. Jour. Inf. Dis., 3, 1906, and loc. cit. 



48 Neufelcl arid Hiine. Arb. a. d. kais. Gesundh. Ami., Vol. 25, 1907. 



