PRACTICAL EXERCISES 



299 



(3) Repeat (i) with the tube connected to the mouth by a glass 

 tube held between the lips, and the nostrils open. 



(4) Repeat (2) with the tube in the mouth and the nostrils closed. 



9. Estimation of the Quantity of Water and of Carbon Dioxide given 

 off by an Animal (Haldanes Method}. (i) Connect the apparatus 

 shown in Fig. 139 with the water-pump. Allow a negative pressure 

 of 5 or 6 inches of water to be established in it, as shown by the rise of 

 water in the bell-jar B. Then close the open tube of carbon dioxide 

 bottle i, and clamp the tube between the water-pump and the bell-jar. 

 If the negative pressure is maintained, the arrangement is air-tight. 

 Now weigh bottle 3 and bottles 4 and 5, the last two together. Place 

 a cat in the respiratory chamber A, connect the chamber directly with 

 the water-pump, and test whether it is tight. Then take the stopper 

 out of bottle i, and adjust the rate at which air is drawn through the 

 apparatus. Let the ventilation 

 go on for a few minutes, then 

 insert bottles 3, 4, and 5 again. 

 Note the time exactly at this 

 point, and after an nour dis- 

 connect 3, 4, and 5, and again 

 weigh. The difference of the 

 two weighings of 3 shows the 

 quantity of water given off by 

 the animal in an hour; the dif- 

 ference in the combined weight 

 of 4 and 5, the quantity of 

 carbon dioxide. Weigh the cat, 

 and calculate the amount of 

 water and of carbon dioxide 

 given off per kilo per hour. 



(2) For the student it is 

 more convenient to use smaller 

 animals. The mouse may be 

 taken as an example of a 

 warm-blooded animal, and the 

 frog of a cold-blooded. Instead 

 of the Woulff 's bottles use wide 

 test - tubes connected 



Fig. 140. Absorption Tubes for CO 2 and 

 Moisture. A, soda -lime tube; B, [sul- 

 phuric acid tube; C, wooden frame, in 

 which A and B are supported by wires d ; 

 '), wire hook, which grips the glass tube 

 firmly, and by means of which the tubes 

 are lifted out of the frame in order to be 

 weighed; a, short piece of glass tubing, 

 by taking out which the absorption tubes 

 are disconnected from the rest of the 



apparatus; e, glass tube going off to animal 

 chamber. 



as in 



Fig. 140, and for the animal 

 chamber a small beaker, closed 

 with a very carefully fitted 



cork which has been boiled in paraffin. The inlet and outlet tubes of 

 the chamber are to be introduced through this cork. The holes for these 

 are to be bored with the greatest care, and the tubes to be put in while 

 the cork is still hot from boiling in paraffin. Also insert a thermom- 

 eter about 6 inches long registering from o C. to 45 C. Modeller's 

 wax is to be used finally to render all the junctions air-tight. 



Add to the series of tubes described in the apparatus a single tube 

 containing baryta-water. This is placed to the left of tube 5, and so 

 arranged that the air-current bubbles through the water. As long 

 as the absorption of carbon dioxide is complete, the baryta-water 

 remains clear. Beyond this a water-bottle should be placed to act 

 as a valve and to indicate the negative pressure in the apparatus. It 

 can be most simply constructed by using a cylinder of stout glass 

 tubing in a wide-mouthed bottle containing some water, the inlet and 

 outlet tubes passing through a paraffined cork which seals the upper 

 end of the cylinder. 



