Degrees of Reaction 141 



different bloods were brought together into sohition, so that each blood 

 in the mixture was diluted to about 1 : 500 or 1 : 000, the presence 

 of other bloods did not impede a reaction taking place between an 

 antiserum and its homologous blood in the mixture. The antiscra only 

 acted however when a suitable blood was present in such a mixture. 

 (For details see original.) Ziemkc (17, X. 1901) subsequently repeated 

 my experiment ' and confirmed it. 



The measurement of Degrees of Reaction. 



In my paper of 21, XI. 1901, p. 152, read before the Royal Society, 

 I mentioned that I had undertaken to make quantitative measurements 

 of the degrees of reaction obtained with precipitating antisera upon 

 different bloods. Owing to the labour involved in the qualitative, 

 and approximately quantitative tests here recorded, a report upon the 

 results obtained had to be deferred. I however described my method 

 in the following year (5, IV. 1902). I shall not dwell upon the method 

 here, but refer the reader to Section VII which follows. As stated in 

 the last paper referred to, the amount of precipitum, say 003 c.c, 

 obtained by adding 01 c.c. of an antiserum to 0'5 c.c. of its homologous 

 blood dilution (1 : 100 or 1 : 200) is taken as 100, and the reactions 

 given by non-homologous bloods are stated in percentages of that figure. 

 At the time I reported two sets of tests, which were, however, not to be 

 taken as final, as follows : 



I only cite these results to show that there are measurable differences 

 in the degrees of reaction, as calculated upon the precipitum obtained 

 with different bloods, the precipitum being actually measured volumet- 

 rically. The method I described has not as yet been tried by workers 

 outside our laboratory. 



^ Ziemke cites my paper but does not state this as well as some other particulars. 



