430 



Mr. H. R Dean. 



[Oct. 13, 



mixture of normal horse serum and the serum of a rabbit which had been 

 injected with horse serum. Both the horse serum and the antiserum were 

 heated for half an hour at 56° C. before use. Since such a mixture of serum 

 and antiserum produces a bulky precipitate it was found necessary to dilute 

 the antiserum to such an extent that only a slight trace of opalescence was 

 produced when it was mixed with the antigen. The antiserum used was 

 found to give a hardly perceptible opalescence in a dilution of 1 in 100. If 

 less diluted antiserum was employed the precipitate formed was so large as 

 to make it impossible to determine if the middle-piece solution took any 

 part in the reaction. The result of such an experiment is shown in Table VI. 



From a consideration of Table VI it appears that a mixture of a normal 

 serum with its homologous antiserum is able to effect the precipitation of 

 some substance present in the middle-piece solution. This effect can only be 

 demonstrated by using a greatly diluted antiserum. As in the agglutination 

 experiments the effect of adding middle-piece solution was only demonstrable 

 if it was added to a small quantity of antiserum. It also appeared that for 

 the effective precipitation of middle-piece it was necessary that there should 

 be present a relative excess of antigen. This is of interest since it is precisely 

 under these conditions that Bordet was able to produce the phenomenon 

 which he called co-agglutination. 



On the Properties of the Globulin Solution prepa red from Sheep Serum. 



The capacity of the middle-piece or globulin solution obtained from guinea- 

 pig serum does not appear to be a peculiarity of the serum of the guinea-pig. 

 Fresh sheep serum was treated with C0 2 in a similar fashion and the resulting 

 solution of the globulin precipitate had the power of increasing agglutination 

 in a suitable mixture of sheep corpuscles and hemolytic antiserum. The 

 result of adding a solution of sheep globulin to a mixture of horse serum with 

 rabbit v. horse serum is shown in Table VII. 



The following mixtures were prepared : — 



Remarks on Table VI. 



Table VII. 



Normal horse 

 serum diluted 

 1 in 10. 



Rabbit v. horse 

 serum diluted 

 1 in 50. 



Sheep middle- 

 piece solution 

 1 in 10. 



Normal saline 

 solution. 



