140 FRANK C. BECHT AND JAMES R. GREER 



PROTEIN PRECIPITINS. 



Since most investigators who have worked with precipitins are 

 agreed as to the delicacy and specificity of the reaction, we chose 

 them as one of the antibodies best suited for study in our work on the 

 body fluids of normal and immune animals. In several cases these 

 were the same animals used in the work on hemolysins and hemag- 

 glutinins. 



Our method was the same as is usually employed, namely, a 

 dilution method. Doses of the immune fluid varying between o . 2 c.c. 

 and o.oi c.c. were placed in a series of test tubes and made up to 

 2 c.c. with sterile 0.9 per cent Nad solution. To these tubes were 

 then added 0.15 c.c. of the same serum as used for immunization. 

 Control experiments were made in case of each of the fluids, and of 

 the serum, to eliminate any possibilities of a sediment from the protein 

 solutions confusing the results. The tubes were incubated for two 

 hours at 37 C., and then left in the ice-box 12 to 20 hours before the 

 final reading was made. 



Our results were as follows: In the fluids of three normal dogs 

 tested with the fresh serum of the rabbit not a trace of precipitate 

 appeared in any tube. 



In experiments with the fluids of seven dogs immune to rabbit 

 blood, three gave positive and four negative results. One dog gave 

 a precipitate only in the first dilution of the serum (i : 10) ; the other 

 mixtures and the control mixtures remained perfectly clear. This 

 animal had been immunized by repeated injections of rabbit blood 

 intraperitoneally, receiving in all 57 c.c. between November 14 

 and December 5, 1908. 



A dog which 10 days earlier had received an intraperitoneal 

 injection of 150 c.c. of rabbit blood gave a positive reaction in 

 both serum and thoracic lymph. In this case the precipitation 

 occurred in a much higher dilution than in the former, tho in the 

 latter, neither the neck lymph, pericardial fluid, cerebrospinal fluid, 

 nor the aqueous humor nor any of the controls showed any pre- 

 cipitate. 



A dog immunized by the intraperitoneal injection of 80 c.c. of 

 rabbit blood gave the best results of all, the serum and thoracic 

 lymph giving precipitation in dilutions of i : 40 and the <neck lymph 



