NUTRIENT MEDIA AND METHODS OF CULTIVATION. 



129 



i"iG. 62.— Aitkbn's 

 Tube. 



and if the contents remain transparent and free from film, they 

 may be set aside as stock-bulbs, to be used when required. 



To inoculate the liquid in the bulb the end of the neck is heated 

 to sterilise the exterior, the bulb is gently warmed, and the extremity 

 of the neck nipped off with a pair of sterilised forceps. The open 

 extremity is plunged into the liquid containing the micro-organisms, 

 and a minute quantity enters the tube and mingles with the fluid in 

 the bulb without fear of contamination by atmospheric germs. The 

 extremity of the neck is once more sealed up in the flame of a 

 Bu nsen burner. 



Aithen's Tubes. — These tubes are plugged and sterilised, and the 

 nutrient medium introduced as into ordinary test-tubes. Instead 

 of withdrawing the cotton-wool plug, they are 

 inoculated through a lateral arm. The sealed 

 extremity of the arm is nipped off with 

 sterilised forceps, and the inoculating needle is 

 carefully introduced through the opening thus 

 made. It is directed along the arm until it 

 touches the opposite side of the test-tube, where 

 it deposits the material with which it was charged. 

 The needle is withdrawn, and the end of the 

 lateral arm again sealed up in the flame ; the test-tube is then 

 tilted until the liquid touches the deposited material ; on restoring 

 the tube to the vertical, the material is washed down with the 

 nutrient liquid. 



Miqtiel's Bulbs. — The tube a 

 houle of Miquel is also a very 

 useful form. It consists of a 

 bulb of 50 cc. capacity, blown 

 in the middle of a glass tube. 

 The part of the tube above the 

 bulb is contracted in two places, 

 and can either be left quite 

 straight or made to curve 

 slightly. Between the contrac- 

 tions the tube is plugged with 

 asbestos. The portion of the 

 tube below the bulb is S shaped, 

 and drawn out at its extremity 



into a fine point. The bulb is charged with nutrient liquid and 

 inoculated by aspiration, and the point of the S tube sealed in the 

 flame of a Bunsen burner. 



9 



Fig. 63.— Miquel's Bdlb. 



