1902.] the Bactericidal Forcer of small Samples of Blood. 67 



-carried across to the vessel which contains the culture, and is filled in 

 with this last up to the mark on the capillar}'- stem. 



Mixture of the serum and culture can now be effected either (a) in 

 the pipette itself, or — and I owe this suggestion to my colleague, Major 

 W. B. Leishman, E.A.M.C., — (b) in a mixing tube such as is shown in 

 fig. 6. 



In the former case, oil in sufficient quantity to seal the lower end of 

 the column of fluid is aspirated into the pipette, after the volumes of 

 serum and culture have been measured in in the manner described. 

 The contents of this tube are then cautiously drawn upwards until the 

 walls of the capillary stem fall away sufficiently to liberate the index 

 globule of oil. This obstacle having been got rid of, a series of upwards 

 and downwards displacements of the combined column of fluid will 

 bring about the desired mixture. 



In the case where a mixing tube is employed, the extremity of the 

 capillary pipette is carried down to the floor of the mixing tube, and 

 the contents are driven out under the covering seal of oil. They are 

 then intermixed by alternately drawing them in and driving them out 

 of the capillary stem, care being taken that the pipette is never 

 emptied of oil. Lastly, the mixed fluids are carefully and completely 

 reaspirated from the floor of the narrowed end of the tube, the inflow 

 being in each case allowed to continue until a sufficient seal of oil has 

 been carried in behind the mixture of serum and culture. As soon as 

 this has taken place, the point of the pipette is withdrawn from the 

 oil, and air is allowed to enter and occupy the lower third of the stem.- 

 Finally, the orifice is sealed in the flame. 



In filling in a succession of capillary pipettes from one and the same 

 mixing tube, it will, as consideration will show, be advantageous to 

 begin with the highest dilution, and to follow on in order with the 

 lower dilutions. 



Procedure for determining the Bactericidal Effect exerted by the Serum in 

 the absence of Air. 



The process of filling in the bulb of the capillary pipette with sterile 

 nutrient broth — a process which is, in the case of the ordinary aerobic 

 procedure described in the previous section, undertaken as a first step 

 in the filling in of the pipette — is, in the case of the anaerobic pro- 

 cedure, undertaken as the final procedure after the serum and the 

 •culture have been in contact for the desired period. 



It is carried out in the following way : — 



Sterile nutrient broth having been placed ready in a covered watch- 

 glass, the capillary pipette which contains the highest dilution of the 

 culture is taken in hand. A negative pressure having been established 

 in its interior by fitting on a collapsed rubber teat, the lower portion 



