46 



SOLID MEDIA 



FIG. 34.- Chamber-land distri- 

 buting flask. 



[The glass tubing is a piece of ordinary-sized glass tubing bent near the 

 end into an obtuse angle and sealed. About half a centimetre from the 

 sealed end a small hole is blown into it through which the serum enters. 

 This is connected with the Cobbett's bulb by a fairly long piece of india- 

 rubber tubing. 



[4. By aspirating through the plugged tubulure the serum can be drawn 

 into the bulb. When the bulb is nearly full, clip 

 the tubing between the flask and the bulb. 



[5. Remove the test-tube enclosing the delivery- 

 tube, and by releasing the clip above it draw off 

 the serum into test-tubes. 



[6. Coagulate the serum (p. 51). 

 [7. Incubate the tubes for 48 hours and reject 

 those which show any growth.] 



[For many purposes, e.g. the cultivation of the 

 diphtheria bacillus, the serum may be further 

 sterilized after coagulation by heating it to 100 C. 

 in the steamer (Chap. I.). 



[If the serum be wanted in the liquid form for 

 future use, it is best to distribute it in small quan- 

 tities into tubes, to heat it to 55-60 C. in the water 

 bath for some time, and then to add a drop or two of chloroform to each 

 tube with a sterile pipette. The chloroform is readily driven off subsequently 

 by heating the tubes to 40-45 C.] 



B. Koch's method. Apparatus required. Prepare beforehand : 



1. Three or four large covered glass dishes each consisting of two halves 

 fitting one into the other, and capable of holding 2 litres. 



Wrap the dishes in paper and sterilize them in the hot 

 air sterilizer at 180 C. The temperature must be raised 

 slowly to avoid cracking the glass. 



2. Chamberland distributing flasks (fig. 34). 



Wash and dry the flasks, carefully seal the pointed 

 tubulure A in the flame, plug the other tubulure B with 

 wool between the constrictions, and sterilize at 180 C. 



3. Half-litre flasks with long necks (fig. 35). Plug and 

 sterilize at 180 C. 



4. Sterile plugged test-tubes. 



Technique. 1. Collect the blood at the slaughter-house, 

 preferably in cool weather, in the sterilized glass dishes. 

 To collect the blood remove the dishes from their paper 

 wrappings, and when the beast is being bled, after letting 

 the blood which first issues flow away, raise the cover of 

 one of them and collect enough blood to fill it three-parts 

 full : then replace the cover. Several dishes should be filled 

 in the same way. 



2. Put the dishes containing the blood in a cool place, 

 but not in the ice chest, because haemolysis may occur and 

 so impart a red colour to the serum. 



3. After about 36 hours the clot will have formed and 



shrunk leaving the serum as a clear fluid on top. Break off the fine point 

 of a Chamberland flask (fig. 34), pass it through the flame of a spirit lamp 

 and avoiding all sources of contamination as far as possible aspirate the 

 serum into the flask. Seal the point in the flame. 



FIG. 35. Flask with 

 neck drawn out and 

 sealed. 



