38 



A rabbit (serum no 1), inoculated with 

 3 cc. of normal horse serum and bled six 

 days afterwards, demonstrated a serum 

 precipitant up to 1/1.000. 



0,5 serum no 1+0,5 of 1/2 etc. 1/256 

 serum no 2. No precipitation. 



0,5 serum no 2-f 0,5 of 1/2 etc. 1/256 

 serum no 1. No precipitation. 



0,5 26th day's seriuii+0,5 of 1/2 etc. 

 1/256 serum no 1. Precip. up to 1/64. 



0,5 26th day's serum-1-0,5 of 1/2 etc. 

 1/256 serum no 2. Precip. up to 1/265. 



A rabbit was inoculated. 



On Feb. 12th 1920 with 15 cc. 

 normal horse serum. 



On Feb. 14th 1920 with 10 cc. 

 normal horse serum. 



On Feb. 16th 1920 with 10 cc. 

 normal horse seriun 



and bled on Feb. 20th 1920. That is 8 

 days after the first injection. 



The serum 1 was precipitant up to 

 1/100.000. 



A rabbit was inoculated with 15 cc. 

 normal horse seriun and bled eight days 

 afterwards. 



Adopting the same critérium as in 

 the previous experiments, the mixture 

 of these two sera gave no precipitation. 



Two rabbits received subcutaueous- 

 ly 15 cc. of normal horse serum and 

 were bled on the 1th and 10th day after- 

 wards. 



One of the sera precipitated up to 

 Î/10.000, the other one which wasslight- 

 iy hemolysed, would not go beyond 

 1/1.000. 



The serial mixture of these two sera, 

 would also not furnish precipitates even 

 using the sera in their natural condition. 



Therefore one concludes that: 



a) Precipitating sera with identical 

 bleeding period, although they should 

 have the same precipitating titre and ve- 

 ry great differences in the quantity of 

 precipitinogen, do not usually precipi- 

 tate when mixed. 



b) Precipitating sera with the same 

 bleeding period, with different precipi- 

 tating titres although with approxima- 

 tely equal quantities of precipitinogen, 

 did also not produce the formation of a 

 ring. 



We must add, however, that some- 

 times upon mixture of precipitating sera 

 with same period of bleeding (10th day, 

 16th day) we would obtain subsequently 

 the slow appearance of a diffuse ring, 

 imdoublely due to a phenomenon of pre- 

 cipitation. 



These reactions were however very 

 weak in comparison with those obtained 

 with sera of different dates in the abo- 

 ve mentioned series. We are therefore 

 led to believe that the incubation terms 

 of the precipitins in the animal species 

 of are only approximately identical and 

 that the character of precision evinced 

 by our experiments is due to the tJie spa- 

 ces of time sufficiently large to exceed 

 individual oscillations. 



5th Series of experiments: 



A rabbit inoculated with 15 cc. of 

 normal horse seriun and bled on the 

 21rst. day, furhished precipitins up to 

 1/10.000. 



This serum mixed with the one of 

 16 days already previouly employed and 

 of a precipitating titre of l/l.OOO.OOO, 

 did not demonstrate precipitation in any 

 of tiie tubes. 



Two rabbits of approximately equal 

 weight were inoculated with 15 cc. nor- 

 mal horse serum and four days later 

 with another 10 cc; seven days after 

 the last injection one of them (n» 



1) was bled of 50 cc. and the other (n» 



2) only of 10 cc. 



The precipitating titre did not exce- 

 ed 1/10.000 and the mixture in any pro- 

 portion of the two sera would not cause 

 the appearence of a ring. Five days af- 

 terwards these animals were bled once 

 more. Nr. 1 serum precipitated only up 

 to 1/1.000, nr. 2 süll up to 1/10.000. 



