MICROLITER DIVER TECHNIQUE 371 



tions regarding the choice of diver type and arrangement of seals 

 under different experimental conditions. Assmned: A diver charge 

 like that used in the measurement of respiration, comprising a 

 reaction mixture (R) containing the organism, an absorption seal 

 (A), a seal of paraffin oil (0), a mouth seal (M). The gas phase 

 consists of air." 



(9) FILLING THE DIVER UNDER ANAEROBIC CONDITIONS 



In their studies on anaerobic respiration in the amphibian embryo, 

 Boell, Needham, and Rogers (1939) employed an apparatus which 

 permitted charging the diver in a nitrogen atmosphere. Holter (1943) 

 described an apparatus which has the advantage of permitting 

 small and narrow-necked divers to be filled more easily under 

 anaerobic conditions. The apparatus of Boell et al. is shown in 

 Figure 131, and that of Holter in Figure 132. 



In Holter's apparatus (Fig. 132) the mercury vessel is mounted 

 on a stand with a rack and pinion so that it can be moved up and 

 down. E shows the base plate, F the diver clamp, and G the mercury 

 vessel. The glass tube {K) must be wide enough to allow the diver 

 to be moved horizontally to bring it under the various pipettes. 

 The gas enters through tubes C and D and goes out through the 

 bubble counter (L) . In the arrangement shown, pipette A is used for 

 an aqueous solution such as sodium hydroxide, pipette B for the oil 

 seal, and C to introduce the gas into the diver. The latter pipette 

 is drawn to an outside diameter of 0.3-0.5 mm. at the tip. The 

 pipettes must be drawn so that the fine stems are precisely coaxial 

 with the main tubes ; only when the stems are parallel to one another 

 will they all fit into the diver. The upper tubes of A, B, and C are 

 heated and cemented together with picein, and, if the pipette stems 

 are parallel, the tube D is joined to the group and they are all 

 sealed air-tight with picein or wax into a wide hole in the rubber 

 stopper. Rubber tubing is connected to the upper ends of the tubes. 

 The liquids which are to be pipetted are placed in small tubes drawn 

 out at the mouth to form a stem thin enough to be held by the diver 

 clamp. 



