100 



BACTERIA 



matter is caught in the sugar. Warm, nutrient gelatine 

 (10-15 cc.) is now poured into the broad end of the tube, 

 and by means of a sterilised stilette the sugar is pushed 

 down into the gelatine, where it quickly dissolves. We 

 have now in the gelatine all the micro-organisms in the air 



SEDGWICK'S TUBE 



Fixed upon Tripod for Air Examination 



which has been drawn through the tube. After plugging 

 with wool at both ends, the tube is rolled on ice or under 

 a cold-water tap in order to fix the gelatine all round the in- 

 ner wall of the tube, which is incubated at room tempera- 



