MICROL-ITER DIVER TECHNIQUE 355 



It is to be used for the determination of the respiration intensity 

 of infusoria and is to contain the following charge: at bottom: 0.8 

 fA. of the infusoria culture medium; in the neck: 0.7 jxl. N/IO NaOH, 

 0.7 ^1. paraffin oil, and a mouth seal 2 mm. long. The inside diameter 

 of the diver's neck is 0.75 mm., its area 0.445 mm.-, hence the volume 

 of the mouth seal 0.89 [A. 0^ the density of the bottom drop and the 

 .V/10 NaOH is practically = 1, 0,,, = 0.87, 0,„ = 1.325, F, = 23.6- 

 12.9 = 10.7 lA. 



10.7 X 1.325 - 0.7 X 0.87 - 1.5 X 1 - 0.89 X 1.325 



yo = 



1 - (1.325/2.40: 

 10.89 



0.448 



= 24.3 mg. 



The weight of the diver may be adjusted by cutting off part of 

 the tail or fusing more glass onto it. If too heavy, a little more of 

 the tail is cut off than necessary and the diver is brought to the 

 proper weight, within 0.1-0.2 mg., by fusing on measured lengths 

 of glass thread of known diameter. Finally, the threads are fused 

 into a ball at the end of the tail, and the diver is dried and weighed 

 to 0.05 mg. 



The weight of the diver is checked by charging it with the 

 quantities of the liquids chosen in the calculation, and determining 

 its equilibrium pressure. If properly prepared, the equilibrium 

 pressure will not deviate more than 20 cm. from the barometric 

 pressure. 



Devices for Holding the Diver. The diver is charged by raising 

 it on a mechanical stand so that the tip of the pipette, which is 

 stationary, can be brought exactly to the position desired and the 

 contents of the pipette discharged at the proper place in the diver. 

 Special diver holders have been described by Holter which facilitate 

 the pipetting manipulations. 



For divers with short necks (^ 1 mm. in width) the simple 

 rubber tubing holder, shown in Figure 119, may be used. For divers 

 with narrow necks, the centering with respect to the stem of the 

 pipette is more difficult, and, accordingly, Holter devised a clamp 

 stand which can be fixed relative to the pipette so that repeated 

 centering is not required. The clamp stand is shown in Figiu'es 120 



