W. B. WHERRY 871 



A crucial experimental test was devised by Wright and Douglas' who saw the 

 necessity of testing the phagocytic power of leukocytes outside the animal body and 

 in the absence of body fluids. Employing a modification of the method of measuring 

 the phagocytic power of the blood devised by Leishman^ they determined that washed 

 leukocytes could not take up bacteria, or did so very poorly, in the absence of some- 

 thing which was present in normal serum. This substance was thermolabile (55° C), 

 was destroyed by Daboia venom and by prolonged exposure to light. This aid to the 

 phagocytes they designated an "opsonic" efifect (opsono, "I cater for"). The elements 

 in the blood fluids which they supposed produce this effect they called "opsonins." 

 Experiments in which bacteria and leukocytes were treated separately with serum and 

 then washed and brought together again showed that the opsonic effect was exerted 

 upon the bacteria and not upon the leukocytes. Bulloch and Atkin found that op- 

 sonin could combine with bacteria at 37° C. or 0° C, and that when such union had 

 taken place even prolonged heating at 60° C. did not alter the effect. These observa- 

 tions were confirmed by many of Wright's pupils and associates, and in this country 

 especially by Hektoen and his pupils.^ 



Neufeld and Rimpau,'' working with sera derived from animals immunized with 

 streptococci and pneumococci and conducting their experiments in vitro, con- 

 cluded that the heated sera (62°-63° C. for forty-five minutes) contained something 

 which altered the bacteria so as to make them susceptible to phagocytosis. These 

 substances they called "bacterio tropins." 



The question as to the identity of the opsonic substances present in normal serum 

 (normal opsonins) and those produced by immunization (bacteriotropins, immune 

 opsonins) has apparently been settled in the affirmative. Normal serum contains 

 small amounts of immune opsonins for various bacteria but this is present in such 

 minute amounts that it requires the aid of complement. When normal serum is heated 

 to 55° C. the complement is destroyed and the serum appears inactive. But, as shown 

 by Cowie and Chapin,^ such heated normal serum may be reactivated by an amount 

 of fresh normal serum which by itself has very little opsonic effect. 



While heated immune serum has an opsonic effect, its action is greatly enhanced 

 by the presence of a little normal serum (Dean,'' Hektoen^). Wright and Reid^had al- 

 ready shown that the apparent relative resistance of immune opsonin to heat or to 

 light was abolished if one diluted it. Therefore the full opsonic action of normal or 

 immune sera is dependent upon the co-operation of two bodies, complement and op- 

 sonin. 



It seems probable — from the absorption experiments of Bulloch and Western'' 



'Wright, A. E., and Douglas, S. R.: Proc. Roy. Soc, 72, 357. 1903; 73, 128. 1904. 



^Leishman, W. B.: Brit. M.J., i, 73. 1902. 



3 Hektoen, L., and others: J.A.M.A., 46, 1407. 1906; ibid., 57, 1579. 1911. 



■i Neufeld, F., and Rimpau, W.: Deutsche med. Wchnschr., 30, 1458. 1904. 



5 Cowie, M., and Chapin, W. S.: /. Med. Research, 17, 57, 95, 213. 1907. 



^Dean, G.: Proc. Roy. Soc, 76, 506. 1905. 



'Hektoen, L.: /. Infect. Dis., 6, 67. 1909. 



* Wright, A. E., and Reid, S. T.: Proc. Roy. Soc, 77, 211. 1905-6. 



9 Bulloch, W., and Western, G. T.: ibid., p. 531. 



