234 



A MANUAL OF BACTERIOLOGY 



They should contain 10,000,000,000 organisms per cubic centi- 

 metre, and thus prepared will keep for some time. 



The patient's (or other) serum is diluted by the drop method, 

 the pipettes of the Dreyer's outfit serving well for this purpose. 

 The dilutions are conveniently made in an artist's porcelain 

 palette with sunk holes or cups ; three rows, each with seven cups, 

 answer best. Into cup No. 1 of a row 4 drops of saline are 

 dropped, and into each of the other cups 2 drops of saline. To 

 cup No. 1 one drop of serum is added and well mixed. Transfer 2 

 drops from the mixture in cup No. 1 to cup No. 2 and well mix. 

 Transfer 2 drops from cup No. 2 to cup No. 3 and well mix, and 



80 160 320 5 10 20 40 80 160 320 5 10 20 40 60 160 320 



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(a) The Agglutinometer Slide. 



(6) The Mechanical Mixer. 

 FIG. 35. Garrow's Agglutinometer. 



so on to cup No. 7. This yields a series of dilutions in cups No. 1 

 to No. 7 of 1-5, 1-10, 1-20, 1-40, 1-80, 1-160 and 1-320. The 

 agglutination is carried out on a plate of glass and by means of a 

 mechanical mixer. The agglutinometer slide consists of a piece 

 of thick clear glass 25 cm. long and 4 cm. broad, with smooth 

 edges. It is divided by double grooves cut crosswise on one 

 surface at regular intervals of 1 cm. The grooves are 1 mm. deep 

 by 1 mm. broad and 1 mm. apart. They divide the surface of 

 the slide into spaces 7 mm. broad and 4 cm. long. These are the 

 spaces on which the agglutination tests are carried out. There 

 are twenty-one " test spaces " on the slide. Each set of seven 



