METHODS OF TESTING FOR AGGLUTINATION 119 



contact with 

 following : 



the bacteria. The stages of procedure are the 



- 



1. Blood is conveniently obtained by pricking the lobe of the ear, 

 which should previously have been washed with a mixture of alcohol 

 and ether, and allowed to 



dry. The blood is drawn /^ 

 up into a Wright's blood- 

 capsule (Fig. 45) or into 

 the bulbous portion of a 

 <-apillary pipette, such as 

 in Fig. 44, a. (These pip- 

 ettes can be readily made 

 by drawing out quill glass- 

 tubing in a flame. It is 

 convenient always to have 

 several ready for use.) 

 The pipette is kept in the 

 upright position, one end 

 liein^ closed. For purposes 

 of transit, break off the 

 bulb at the constriction 

 and seal the ends. After 

 the . serum has separated 

 from the coagulum the 

 bulb is broken through 

 near its upper end, and tlie 

 serum removed by means 

 of another capillary pip- 

 ette. The serum is then 

 to be diluted. 



2. The serum may be 

 diluted (a) by means of a 

 graduated pipette either 

 a leucocytorneter pipette 

 (Fig. 44, 6) or some cor- 

 responding form. In this 

 way successive dilutions 

 of 1 : 10, 1 : 20, 1 : 100, 

 etc. can be rapidly made. 

 This is the best method. 

 (b) By means of a capillary 

 pipette with a mark on the 

 tube, the serum is drawn 

 up to the mark and then 

 blown out into a glass 

 capsule ; equal quantities 

 of bouillon are successively 



measured in the same way, and added till the requisite dilution is 

 obtained, (c) By means of a platinum needle with a loop at the end 

 (Delepine's method). A loopful of serum is placed on a slide, and the 

 dfsiwl number of similar loopfuls of bouillon are separately placed 

 around on the slide. The drops are then mixed. 



A very convenient and rapid method of combining the steps 1 and 2 



FIG. 44. Tubes used in testing agglutinating 

 and sediinenting properties of serum. 



