2()2 LOCAL ILSSLL RL/VCIIVLIV 



j)r()j)()rli()iis yifldiiio miiiiimim and nicdiinn aiiioimls ol precipi- 

 tation) , bolli the j)rccijMtatcs and the siij^einalant lliiids Avere ])0- 

 tent. 1 he supernatant Ihiids \veie clear at the time oi the injec- 

 tions, namely, the day iollowino pre])aration. SujDernatant fluids 

 winch were derived Irom comj^letely jjrecipitated mixtures re- 

 mained clear tor an indefinite length of time. The supernatant 

 fluids derived from j^artially precipitated mixtines became clotidy 

 alter several days in the refrigerator. The latter preparations were 

 re-centrifuged t\vo to three times in the cotnse of the following 

 week. When no more cloudiness appeared in the refrigerator, 

 they were foinid on retest totally devoid of reacting potency. It 

 (ould he asstniied, then, tliat the reacting potency of supernatant 

 fluids derived from partially precipitated mixtines may be due 

 either to grossly visible precipitates or to a precipitation occurring" 

 upon injection into the blood stream. It is obvious, however, 

 from the alcove that the reacting potency of a given preparation 

 does not depend either on the amoinit of the precipitate obtained 

 or on the size of the aggregate formed /// niho. 



ZONE REACTIONS IN ANTIGEN-|- ANTIBODY COMPLEXES IN RELATION 

 TO THEIR REACTING POTENCY 



According to Fleischmann and Michaelis (quoted loy Wells) 

 the formation of precipitate occurs according to the following 

 rules: 



1. With a given quantity of precipitinogen, the amount of pre- 

 cipitate increases with increase in the quantity of precipitin; 2. 

 With a given quantity of precipitin the amount of precipitate in- 

 creases at first with addition of precipitinogen, then decreases, and 

 w'hh a certain excess of the latter approaches zero, this being the 

 zone phenomenon; 3. With constant amounts of both, the quan- 

 tity of precipitate decreases as the amount of ffuid in vvhich the 

 reaction takes place increases. The zone phenomenon is observed 

 not only wit|i isolated serum proteins but also vvith crystallized 

 egg albtmiin and vvith meningococcus carbohydrates. Recent ob- 

 servations of GoldsAvorthy and Rudd (19.^55) clearly demonstrate 

 the presence of multiple zone phenomena in crude sera (prozone 

 and interzone reactions) . 



The single and multiple zone reactions are of rather irregular 

 occurrence in formation of reacting factors by antigen-^antibody 

 complexes. This may be illustrated by the following two ex- 

 amples: 



