RESPIRATORY MOVEMENTS IN THE MAMMAL 



287 



huret is nitrogen. Compute the amount of carbon dioxide, oxygen, and 

 nitrogen from the results of your test. 



Expired Air. Take a large sample of expired air by breathing through 

 a large tube into a gallon aspirator bottle. This is large enough to hold 

 six or eight expirations. Now fill the gas buret with a sample of this expired 

 air and analyze as before, first for carbon dioxide, then for oxygen; com- 

 pute the percentage of each gas, including nitrogen. The expired air will 

 usually be found to have lost from 4 to 5 per cent of oxygen and have gained 

 a little more than that quantity of carbon dioxide. 



From the percentages obtained in these experiments, and the volume 

 of air breathed per unit of time, computed in experiment 4 above, determine 

 the amount of carbon dioxide exhaled per hour per kilogram of weight for 

 your own body. Compute also the amount of oxygen consumed. 



9. The Rate and Character of ttie Respiratory Movements in the 

 Mammal, a, The rate of respiration can be best determined by 

 direct count per minute, an effort being made to keep the animal under as 



FIG. 245. Arrangement of Tracheal Cannula and Marey's Tambour for Recording the Changes 

 in Intratracheal Pressure during Respiration. (Langendorff.) 



nearly normal conditions as possible; make the same determinations on a 

 cat, a dog, and guinea-pig, b, The character of the respiratory movements 

 can be recorded by one of the various forms of stethograph adapted to the 

 size of the animal, or by the arrangement shown in figure 245. It is usually 

 better to make the determination with the animal under the influence of an 

 anesthetic. 



10. The Determination of Carbon Dioxide Given Off in the Mam- 

 mal. This determination can be made only by placing the animal 

 in a respiratory calorimeter, and making the following measurements: 



a. The amount of air which passes through the animal chamber, the 

 calorimeter. 



b. The percentage of carbon dioxide in the air which is in the chamber. 



