76 



A MANUAL OF BACTERIOLOGY 



duce a small pledget of sterilised wool into each, push 

 to the bottom, and moisten with a little sterilised distilled 

 water. Drop the potato-wedges into the tubes, plug, 

 and sterilise by steaming for three-quarters of an hour 

 on two successive days (Fig. 9 B). The object of the moist 

 wool is to prevent drying, and for the same 

 ^oT2j^ purpose Roux's tubes (Fig. 10) may be used, 

 the lower bulb being filled with water. 



Blood-serum. Clean some glass jars of 

 about 1 to 3 litres capacity, plug with wool, 

 and sterilise in the steamer for an hour on 

 three successive days. Bleed a horse, with 

 aseptic precautions, and catch the blood in 

 these sterilised jars. Allow the jars to stand 

 in a cool place for twelve hours. Then 

 pipette off the clear serum with a sterile 

 pipette, and fill the sterilised test-tubes to 

 the depth of 2-4 cm. The tubes are then 

 arranged in a sloping position on the shelves 

 of the serum inspissator, or failing this in a 

 hot- water oven, the temperature of which 

 should be about 50 C. At this temperature 

 they remain for thirty hours ; it is then 

 raised to 65 C., at which temperature the 

 serum coagulates in from four to six hours 

 and the tubes are now ready for use. It is 

 well, however, to place them in the blood- 

 heat incubator for a night, so that any 

 contaminating bacteria may form colonies, and the con- 

 taminated tubes may then be rejected. Ox or sheep blood 

 may also be used and may be obtained from the slaughter- 

 house ; the corpuscles do not separate so well. 



Loffler's blood-serum is prepared by adding one part 

 of glucose broth to three parts of the serum before 

 inspissation. 



FIG. 10. 

 Roux's tube 

 for potato. 



