56 PATHOGENIC BACTERIA 



be collected in a pipette of the kind represented in the adjoin- 

 ing wood cut (Fig. 5), by breaking off the sealed ends of the 



Fig. 5. Pipette containining blood which has separated into clot and serum, the 

 former occupying the lower half of the bulb (nat. size). 



capillary to be on either side of the bulb, and applying one end 

 to the issuing blood. When the expanded part is filled, the ends 

 are hermetically sealed in the edge of the flame of a spirit-lamp. 

 Blood so stored can be tested at leisure, and (if kept in the dark) 

 retains its qualities for long periods. Even if dried the blood 

 will provide the reaction; for this purpose it is collected on a 

 series of cover-glasses, which, after being allowed to dry, may 

 be, if necessary, posted to an expert for examination. If dried 

 blood is used, a solution of the specific substances in it is ob- 

 tained by means of distilled water; but the method is an inferior 

 one, owing to the difficulty of estimating the dilution reached 

 a matter of cardinal importance. 



Nine loop-fulls* of the filtered broth culture of typhoid are 

 placed separately and fairly close together on an ordinary micro- 

 scopic slide, the loop or ose being introduced as many times into 

 the broth. The platinum wire is now sterilized in the flame, 

 and with it a single loop of the blood serum is transferred to the 

 slide and well mixed up with the whole of the nine droplets of 

 broth culture. If the test is carried out on the spot, a few drops 

 of blood may be allowed to flow from the lobe of the ear or fin- 

 ger, and to clot in a small test tube or a watch-glass; the serum 

 so furnished will be ample. 



* For a figure of the " loop," see p. 26. 



