308 Drs. D. A. Welsh and H. G. Chapman. On the [Apr. 30, 



This experiment is somewhat unsatisfactory, for two reasons — the time 

 intervals were not adjusted to ensure completion of each interaction, and the 

 amount of superfluid removed at each stage was not accurately determined. 

 We would not have recorded it at all, were it not for the fact that it is the 

 only indication we have met that the homologous proteid may be diminished 

 as a result of interaction with its precipitin. Even so it is not until after 

 the third interaction that any diminution of homologous proteid is indicated, 

 and we are unable to decide whether that is due to the proteid having been 

 used up to any appreciable extent, or to its amount having been so reduced 

 by successive subdivisions that it is no longer sufficient to produce the full 

 precipitate from 0-01 gramme of this antiserum. 



The cumulative evidence of these and other experiments, all of which give 

 concordant results, renders it increasingly difficult to trace the precipitum to 

 an origin other than the antiserum itself. Presumably the " precipitable " 

 substance in the antiserum is the body commonly known as the precipitin. 

 In any interaction, however, it is the homologous proteid that in some way 

 renders the precipitin insoluble, and this it does without sensibly diminishing 

 its capacity for further effective interaction with fresh precipitin. 



Comparison of Antisera Prepared in the Babhit with Natural Habbit Serum. 



Being led by our observations to the conclusion that an antiserum, prepared 

 in a rabbit by repeated injections of some alien proteid, contained a substance 

 or substances in sufficient abundance to yield definite precipita when thrown 

 out of solution by interaction with the homologous proteid, which substance 

 or substances the natural serum of the rabbit did not contain, we began a 

 series of experiments to determine whether or not it were possible to obtain 

 evidence of other differences between antisera and natural sera from the 

 rabbit besides those revealed by precipitin tests. 



Table XL 



Weight in grammes of 

 5 c.c. of natural rabbit 

 sera (when dried). 



Average 

 weight. 



Weight in grammes of 5 c.c. 

 of antisera prepared in 

 rabbit (when dried). 



Average 

 weight. 



-49371 

 -4681 | 

 -4471 \ 

 -4228 | 

 -3998 J 



gramme. 

 0-446 



-5273 (ox serum) 1 

 0'5174 (horse serum) 

 -5118 (ostrich egg I) [ 

 -4980 (ostrich egg II) j 

 -4878 (hen egg I) 

 -4675 (hen egg II) J 



gramme. 

 0-501 



