60 Prof. A. E. Wright. On the Measurement of [Aug. 5, 



The dilutions are to be held ready for use in a series of covered 

 sterile watch-glasses. 



(3.) Description of the Special Form of Capillar}) Testing Pipette 

 Employed in the Connection with the Method of Bactericidal Estima- 

 tion here described. 



Fig. 4 shows the particular form of capillary testing" pipette which 

 has been found most suitable. The stem A — it will be noted 

 that it is provided with a pencil mark — serves on the one 

 hand as a measuring pipette for measuring off equivalent 

 volumes of serum and bacterial culture, and on the other 

 hand as a receptacle for the combined volumes of fluid during 

 the period allotted to the action of the serum upon the 

 c culture. 



The bulb B functions, in the first stage of the procedure 

 described below, as a receptacle for the sterile broth after- 

 B wards used for testing the continued vitality or otherwise of 

 W the bacteria which have been exposed to the influence of the 

 serum. In the second part of the procedure, the bulb of the 

 pipette comes into use as a cultivation chamber. The bulb 

 may conveniently possess a capacity of about 1 c.c. The 

 A spiral C* serves to prevent any access of contaminating 

 bacteria to the interior of the bulb. 



(4.) Method of Employing the Capillary Testing Pipettes. 



The method of employing the testing pipettes is as 

 follows : — 



A mark with the coloured oil pencil having been placed 

 upon the capillary stem at any convenient point, say at a 

 point 1 — 1*5 cm. from the lower end, a rubber teat is fitted 

 over the upper end of the tube. 

 The jjoint of the capillary stem is now broken on 7 between finger 

 and thumb, the lower portion is sterilised in the flame, and the air is 

 expelled from the teat. 



Sterile broth, which has been placed ready to hand in a covered 

 sterile watch-glass, is then aspirated into the pipette until the bulb is 

 about two-thirds full. 



The extremity of the capillary stem is now withdrawn from the 



# It will be found that the introduction of the spiral avoids the necessity for the 

 troublesome plugging of the tube with cotton wool and the subsequent sterilisa- 

 tion process. The very simple trick of hand by which the spiral is made may be 

 readily learned by imitating the motions associated with the making of a similar 

 spiral upon a stiff cord or a very pliable wire. 



