1911.] On the Factors Concerned in Agglutination. 421 



1 in 20 suspension of red cells, with one volume of a 1 in 200 dilution of 

 heated antiserum, was added one volume of 1 in 10 middle-piece solution, 

 an almost instantaneous and very marked agglutination of the red cells 

 took place. On slanting the tube the red cells could be seen to be 

 aggregated in large clumps. The clumps rapidly increased in size, and after 

 20 minutes to half an hour had settled to the bottom of the tube to form 

 a single mass which somewhat resembled a soft clot. The supernatant 

 fluid was left quite clear. The viscous mass which formed at the bottom 

 of the tube could be disintegrated by vigorous shaking, but rapidly re-formed, 

 and the process of shaking the clump apart and allowing it to re-form 

 could be repeated indefinitely. One series of tubes was preserved for 

 48 hours without any change in the condition of the corpuscles. The 

 appearances presented corresponded closely to the description recently given 

 by Bordet and Gengou (1911) of the phenomenon which they called 

 co-agglutination. 



It must be plainly stated that the action of the solution of middle-piece 

 is to accentuate the feebly agglutinative action of a small amount of specific 

 antiserum. An agglutination quite as marked and apparently identical in 

 nature could be produced by using a larger quantity of the antiserum 

 without the addition of middle-piece. The action of middle-piece appeared 



Table I. 





1 c.c. of dilution 

 of hemolytic 



Eabbit v. Sheep, 



+ 1 c.c. middle-piece solution diluted. 



+ lc, 

 normal 

 saline. 



1—10. 



1—20. 



1—40. 



1-80. 



1—160. 



1 



1—10 



+ + + + 



+ + + + 





+ + + + 



+ + + + 



+ + + + 



2 



1—20 





+ + + + 





+ + + + 



+ + + + 



+ + + + 



3 



1—40 



+ + + + 



+ + + + 



llll 



+ + + + 



+ + + + 



+ + + + 



4 



1—80 



+ + + + 



+ + + + 







+ + + 



+ + 



5 



1—160 











+ 





6 



1—320 



+ + + + 



:::: 





+ + 











7 



1—640 



+ + + 





+ 















8 



1—1280 



+ + + 





















9 



1 c.c. normal saline 



























Each tube contained a volume of 3 c.c. made up of 1 c.c. of a 1 in 20 suspension of washed 

 red cells of the sheep, 1 c.c. of a dilution of heated hamiolytic serum (rabbit and sheep), and 

 1 c.c. of the diluted middle-piece solution. The tubes numbered 9, in each row, contained no 

 immune serum and the bulk was made up to 3 c.c. by the addition of 1 c.c. of normal saline 

 solution. In these tubes no agglutination occurred, the middle-piece solution by itself being 

 unable to agglutinate the red cells. The tubes in the last column contained 1 c.c. of the 

 suspension of red cells, 1 c.c. of a dilution of the hamiolytic serum and 1 c.c. of normal saline 

 solution. The agglutinative power of the immune body acting by itself is shown in this column. 

 In the remaining columns is shown the effect of the combined action of the immune body and 

 the middle-piece solution. 



