118 SPECIAL PH YSIOL OGY 



Geissler's potash bulbs, with CaCl 2 tube ground on (g) ; two small 

 flasks (6, h) with rubber stoppers, double bored, with delivery tubes 

 fitted as shown in figure; a 1-litre or 2-litre bottle with very wide 

 mouth to use as animal cage, fitted with delivery tubes and with a 

 cork impregnated with paraffin; siphon apparatus, as figured, consist- 

 ing of two 8-litre bottles with paraffined corks and tubes ; analytical 

 balances; laboratory balances (correct to 0.01 grm.); drying oven; 

 chemicals, KOH, Ba(OH) 2 , CaCl 2 ; any small animal whose weight 

 in grams does not exceed one-fifth the volume of the animal cage 

 expressed in cubic centimetres. 



2. Preparation. (1) Fill the calcium chloride tubes; put them 

 into the drying oven, where they are to be kept at a temperature of 

 100 to 120 C. for several hours; cool in a desiccator and weigh upon 

 the analytical balances the tubes e and /, recording the weight in 

 milligrams. 



(2) Fill the Woulffe bottle and the Geissler's bulbs with a strong 

 solution (50 per cent, or more) of KOH. Fix into position, upon the 

 Geissler bulb, its filled and desiccated CaCl 2 attachment, and fit 

 to each end a rubber connecting tube; clamp with strong serre-fine 

 forceps and weigh upon the analytical balances. 



(3) Fill the flasks b and h with a strong solution of Ba(OH) 2 . 

 These flasks serve simply to show whether or not the CO 2 gas has 

 all been absorbed by the KOH through which it has just passed. 



(4) Pieces e, f, and g should be fixed to a light wooden rack, by 

 which they may be moved; if this is not convenient clamp them to 

 supports. 



(5) Join up the apparatus a, 6, and c. 



(6) Fill siphon apparatus. 



(7) Weigh the animal cage without the animal. 



3. Operation. (1) Put the animal into the cage; fasten the 

 stopper in so that it will not leak air. 



(2) Join the animal cage with c and with siphon apparatus at t*,< 

 leaving out for this preliminary operation the apparatus e, /, g, and h. 

 Start the siphon and note the rate of flow per minute. The level 

 of the water in the lower bottle should be probably 1 metre below 

 that in the upper bottle. Notice whether the animal seems to be 

 respiring normally. If so, it may be taken for granted, after ten 

 minutes, that the ventilation is sufficient. If it seems insufficient, 

 one has only to increase the difference of level in the two siphon 

 bottles. 



(3) Disjoin the animal cage and weigh the cage with the contained 

 animal upon the laboratory balances. Note the time; join the animal 

 cage in circuit again, attaching it to e, and attaching h to the siphon 

 apparatus at i. Start the siphon. The greater resistance to be 

 overcome will necessitate a greater difference in the level of the 

 two bottles in order to ventilate at the same rate as before. To 



