GARROW'S AGGLUTINOMETER 235 



test spaces may conveniently be separated from one another by 

 three grooves (see Fig. S5, a). The mechanical mixer consists 

 of a mechanical contrivance by means of which the agglutino- 

 meter slide is made to revolve on its long axis slowly (about ten 

 revolutions per minute) in an atmosphere saturated with aqueous 

 vapour. The moist chamber is a cylinder of celluloid placed 

 horizontally, the upper half being jointed to form a lid, the lower 

 half lined with filter paper soaked with water. The revolving 

 movement is obtained by means of a simple clockwork attached 

 at one end of the cylinder. The clockwork is self-stopping every 

 fifty revolutions i.e. every five minutes (see Fig. 35, b). 



The moist chamber may be dispensed with in a cool room*, and in 

 the absence of clockwork the rotation maybe performed by hand. 



The process is carried out as follows : Using a Donald's pipette, 

 Morse gauge 70 (see p. 58), which is held vertically, begin with 

 the highest dilution (1-320) and deposit single drops of the series 

 of dilutions of serum each at one end of a test space on the agglu- 

 tinometer slide. If agglutination is to be done on two or three 

 organisms, the drops may be deposited in duplicate or in triplicate 

 on the two or three divisions of the agglutinometer slide. Opposite 

 each drop of serum dilution a drop of bacterial emulsion is de- 

 posited at the other end of the test space (see Fig. 35, a). Thus, 

 in a typhoid-like infection the patient's serum would be tested with 

 typhoid and paratyphoid A and B emulsions (see Fig. 35, a, 1 T, A, B). 



The slide so loaded is placed carefully in the moist chamber of 

 the mechanical mixer, where it is received and held fast by a clip 

 at each end. The clockwork is started by means of the lever, and 

 the slide allowed to revolve slowly till the clock stops after com- 

 pleting fifty revolutions of the slide. 



When the slide begins to revolve the various drops of diluted 

 blood serum run into and mix freely with their corresponding 

 equal drops of bacterial emulsion, producing mixtures having 

 serum titres &, ^, ^, ^fe, T ^, ^, ^. 



At each complete revolution of the slide the bulk of these mix- 

 tures runs to and fro across the slide. 



When the clockwork stops, the agglutinometer slide is removed 

 and examined by the naked eye (aided, if necessary, by a pocket 

 lens) in a good light against a black background. Agglutination 

 converts the mixtures from homogeneous milky emulsions into a 

 condition in which the agglutinated masses of bacilli float about 



