NATURE OF OPSONIN. 329 



to 60 C. Dean, Cowie and Chapin, and others 

 have shown, however, that the opsonic power of 

 heated serum may be increased by the addition of 

 normal serum similar to that reactivation taking 

 place on adding complement to amboceptor. 

 Browning has pointed out that this apparent sim- 

 ilarity of the action of normal serum on heated 

 opsonin may be due to summation of effects. He 

 has shown that by separating immune body in 

 opsonic serum at C. by saturation with bacteria 

 and then adding complement there is a true activ- 

 ation, and that no such action occurred in treating 

 the bacteria with complement, washing and then 

 adding heated opsonic serum. He concludes that 

 immune body and complement may be concerned 

 in opsonic action, but leaves open the question of 

 whether the immune body is the thermostabile 

 opsonin or not. 



Hektoen concludes from the following facts that opsonins as 



-,. ,. , ,. ,, , ., T Distinct 



opsonins are distinct irom other antibodies. Antibodies. 



1. Heat may almost completely destroy the 

 opsonic power of serum leaving the lytic ambo- 

 ceptors intact. 



2. Serum, normal as well as immune, may con- 

 tain opsonin for a given organism but not, at least 

 so far as is known, the proper lytic amboceptor for 

 that organism. 



3. A serum may contain opsonin for an organ- 

 ism, but no agglutinin and the opsonin may persist 

 after destruction of bacteriolytic complement by 

 heat. 



4. In immunization lytic and opsonic powers do 

 not run parallel. 



