Gay and Rusk.] THE LOCUS OF ANTIBODY FORMATION. 5 



Certain by-products of the investigation are in themselves of distinct 

 interest, although their results are negative in so far as explaining 

 antibody formation is concerned. Two incidental investigations 

 may first be summarized before dealing with the work that bears 

 more directly on the site of antibody formation : 



I. THE EFFECT OF IODIPIN ON THE OUTPUT OF ARTIFICIAL HEMOLYSINS. 38 



Muller's 20 experiments led him to the conclusion that both nor- 

 mal sensitizer (amboceptor) and alexin are formed in the liver, 

 but that their output depends on the stimulating action of the 

 iodin of the thyroid gland. This author finds that the injection of 

 thyroid preparations, or of various iodine preparations, notably of 

 iodipin (Merck, 25 or 10 per cent of iodin), produces a distinct 

 increase in from 24 to 36 hours of the normal hemolysins in rab- 

 bits and other animals. As already stated, this increase comprises 

 not only an increase in alexin, as tested on blood cells sensitized by 

 an artificial hemolysin, but an increase of the normal hemolytic 

 sensitizer. Hektoen 21 has further found an increase in hemolytic 

 sensitizers in dogs that received a single dose of goat's blood over 

 the amount produced in control dogs on giving injections of sodium 

 iodoxybenzoate. This alleged increase of normal hemolytic sensi- 

 tizers immediately suggested the importance of determining the 

 effect of iodin on artificial hemolysins, not only as a matter in itself 

 of theoretical and perhaps of practical importance, but as bearing 

 on the origin of antibody formation. Differences that might appear 

 in the hemolytic potency of the sera of immunized animals would 

 presumably be more striking than corresponding differences in nor- 

 mal hemolysins, owing to the much greater strength of immune sera. 



Our experiments deal, first, with the effect of a single injection of 

 iodipin (Merck, 10 per cent) in rabbits that had been immunized by 

 several injections of washed guinea-pig corpuscles. In several ex- 

 periments a control animal that had been immunized in a similar 

 manner, but that received no iodipin, was carried through. The 

 animals with and without iodipin were bled before injection from the 

 ear and at intervals subsequently; the separate sera were heated at 

 once to 56 for one-half hour, and at the end of the experiment all 

 were tested for hemolytic units at the same time with the same cor- 

 puscles and alexin. In other experiments a critical intravenous re- 

 injection of the antigenic blood was given in two highly immunized 

 rabbits, and on the following day one of them was given iodipin. 

 Both sera were then tested at intervals for hemolytic potency. There 

 was no evidence from any of these experiments that the injection of 

 iodipin will increase the output of artificial hemolysins in the im- 

 munized rabbits. 



