9 



v / 



FIG. 86. MACROSCOPIC AGGLUTINATION REACTION. SHOWS ACTION OF AGGLUTIN- 



OIDS (PRO-AGGLUTINATION). 



Note absence of agglutination in dilution 1 : 50; agglutination beginning in 1 : 100, 

 and fairly well marked to 1:4000 inclusive. Note uniform cloudiness of control. 

 This reaction was set up with a typhoid immune serum over six months of age; the 

 drawing was made after the tubes had been incubated two hours and placed in a 

 refrigerator overnight. 



