Observations by F. G. Hopkins 89 



indebted for the loan of his notes, the experiments not having as yet 

 been published. The animals were treated by me with substances 

 supplied by Mr Hopkins. 



Observation I. Two rabbits were treated with intraperitoneal in- 

 jections of crystalline egg albumen, receiving 5 injections, the total 

 volume injected representing 45 c.c. The animals were bled 11 days 

 after the last injection (22, vn. 1901). 



The two antisera were mixed. The mixture remained clear on 

 standing. 



35 c.c. of antiserum were fully precipitated by crystalline egg albumen 

 solution, the amount of which was not determined. 



The dried precipitum weighed only '0246 g. 



Observation II. Three rabbits similarly treated to the above, except 

 that one received 35 c.c., and that the animals were bled 7 days after 

 the last injection (27, vn. 1901). 



The three antisera remained clear when mixed. 



50 c.c. of antiserum were fully precipitated and the dried precipitum 

 weighed "0325 g. 



Observation III. Two rabbits were treated with ox-serum, receiving 

 5 injections of a total amount of 45 c.c. intraperitoneally. Bled 23, v. 

 1901. 



The two antisera remained clear when mixed. 



When the antiserum was added to undiluted ox-serum, drop by 

 drop, the instantaneous precipitum produced was redissolved on stirring. 

 Ten c.c. of ox-serum requiring 5 6 drops of antiserum before permanent 

 clouding was obtained. Evidently then a precipitum is soluble in excess 

 of serum. (See Antiprecipitins, p. 149.) 



The ox -serum was next added to the antiserum. When 6'5 c.c. of 

 ox-serum had been added to 30 c.c. of antiserum no further precipitation 

 occurred, and there was no further clouding subsequently when more 

 antiserum was added to the clear supernatant fluid. The total pre- 

 cipitum obtained from the above mixture of 30 c.c. antiserum and 6'5 c.c. 

 ox-serum, weighed when dried at 110C. '553 g. Prior to drying, it 

 should be added, the precipitum first obtained with the aid of the 

 centrifuge had been thoroughly washed with 5 / NaCl solution, being 

 resuspended and recentrifugalized three times in saline, this being fol- 

 lowed by repeated washings with water, the washing being similarly 

 conducted, until the washings gave no trace of biuret or xanthoproteic 



