532 A CONTRIBUTION TO THE STUDY OF THE PRECIPITINS, 



up to a maximum. Under certain conditions, Arrhenius and 

 Hamburger have found that a precipitate may diminish again. 



(Some qualitative experiments may be quoted first. A series 

 of tubes were arranged containinc; from 0-05 to 0-000000005 em 

 dried horse-serum dissolved in 0-5 c.c. saline solution (0-75 per 

 cent, sodium chloride) so that the dilution of the dried horse- 

 serum in 0-5 c.c. saline solution varied from 1 in 10 to 1 in 

 10,000,000. A control tube containing 0-5 c.c. saline solution 

 alone was also prepared. To each tube of the first series and to 

 the control was added O'Ol gm. dried antiserum (prepared in a 

 rabbit by the injection of 4*4 gm. dried horse-serum in 8 doses) 

 previously dissolved in 0"5 c.c. saline solution. The precipitates 

 were read in 48 hours by measuring the length of tube occupied 

 by the precipitate. A record of the readings is given in Table i. 



Table i. 



From this Table it is evident that in tubes 1, 2, 3, and 4 

 maximal precipitates have been produced, while in tubes 5, 6 and 

 7 submaximal precipitates have been formed. After 48 hours 

 the superfluids above the precipitates were removed and 0-2 c.c. 

 fi'om each tube was placed in a clean tuVje. To each of these 

 tubes containing superfluid, O'OOOl gm. dried horse-serum dis- 

 solved in 0-5 c.c. saline was added. After 48 hours the readings 

 of these secondary interactions were taken. They are recorded 

 in Table ii. 



