RESPIRATION 





4. The Volume of Air Breathed by Man. Determine the average vol- 

 ume of air breathed per respiration, using Hutchinson's spirometer, figure 

 235, set the instrument at the zero point, exhale into the instrument 



through the tube, using all possible care 

 Ml to breathe with your normal rate and 



I 



; ' ~ ; depth. Better results will be obtained 



dgfe|&j by taking the average from sets of ten 



j ? consecutive expirations into the instru- 



^^ ment. From the average of the volume 



per respiration, and the average number 

 of respirations per minute, determined 

 in Experiment i, calculate the amount 

 of air breathed per hour and per day. 

 5 . Vital Capacities. Using the spiro- 

 meter as in the preceding experiment, 

 set the instrument at zero and exhale 

 into it: 



a. Begin with the fullest possible 

 inspiration and exhale the greatest pos- 

 sible amount of air from the lungs. This 

 is known as the vital capacity. 



b. Beginning at the end of an ordi- 

 FIG. 245. Thoracograph of Deufestcl. nai T expiration exhale into the instru- 

 ment the greatest possible amount. 



This is called the reserve air. 



c. Following ordinary inspiration exhale into the instrument until you 

 reach the ordinary state of expiration. This involves the conscious fixing 

 of two points in the respiratory act, namely, the summit of inspiration and 

 of expiration, which are ordinarily automatically adjusted by the body. 

 The error of the determination is therefore great. It is better to make this 

 measurement in sets of ten, as in the preceding experiment, and take the 

 average. This reduces the error. This quantity of air is known as the 

 tidal air. One can measure the tidal air and the reserve air together, check 

 them against the sum of the two, as in a and b. 



d. The sum of the tidal and reserve air taken from the vital air will 

 leave the amount which one may inspire over and above that in the chest 

 at the end of ordinary inspiration. This is called complemental. The 

 complemental can be measured by inspiring the air from the spirometer, 

 but this is not good hygienic practice where large numbers are using the 

 same instrument, unless the instrument be thoroughly cleaned before the 

 inspiration is taken. 



6. The Respiratory Pressure in Man. Measure there spiratory 

 pressure, the variation in pressure of the air in the air-passages, by means 



