434 



Major P. S. Leiean 



[April 



which follows admixture with immune serum diluted one thousand 

 times. The reaction is regarded as complete if at the end of half 

 an hour no separate motile organisms can he seen. The concentra- 

 tion of agglutinins in a serum is measured by the extent to which 

 the serum can be diluted without losing its power to " clump " a 

 culture in half an hour. By means of capillary pipettes, as little as a 

 ten-thousandth part of a drop of blood may be proved effective. 



As normal serum has a slight agglutinative power, which seldom 

 exceeds that represented by a dilution of 1 in 10, that amount is 

 taken as the basis of comparison. We are now in a position to follow 



DAYS 



AGGLUTriNATION CLRVE ^^^^^ I 

 GROUP OF 6 MEN \(2)lOOO 



© 500 MILLION I 



.3000 

 ^2500 

 2000 

 1500 

 1000 

 500 



Fig. 2. — Chaet showing Production of Agglutinins as a Result of 

 Anti-Typhoid Inoculation. 



on our chart the effects of inoculation on the deo'ree of this reaction. 

 {Vide Fig. 2.) 



On the day of the first injection the agglutination power is 

 charted at the 1 in 10 level. There it remains until the eighth day, 

 when there appears a rise which progresses to its maximum of 1:^0 

 times the normal on the thirteenth day, after which it begins to fall. 



It was hoped at first that increase of the single -injection dose 

 would give a proportionately higher rise in the curve, but it was 

 found that increased injections gave little better results, even if 



