134 PRACTICAL PHYSIOLOGY 



The Effect of Muscular Exercise upon the Respiration is very 

 great ; within a few minutes, varying according to the severity 

 of the work and the condition of the subject, the volume of air 

 breathed may be trebled, the number of breaths showing a smaller 

 increase. The breathing is deeper, and the mouth is opened to 

 diminish the resistance to the passage of the air in and out of the 

 chest. Discomfort or distress is caused by any resistance, and for 

 this reason it is impossible to determine the true volume unless the 

 resistance of the recording apparatus is low. Place an " anaesthetic " 

 bag between the meter and the tube from the mask in order to 

 reduce the resistance and determine the volume and rate of respira- 

 tion before and after running down and up a flight of stairs. 



FIG. 131. Stethograph. 



A, Metal drum ; B, hooks for tapes which pass round neck ; C, rubber discs ; D, hooks for 

 attaching tapes which are tied roimd thorax ; E, tube leading to the recording tambour. 



The Graphic Record of the Respiratory Movements. 1 For this 

 purpose an instrument known as the stethograph is used. There 

 are various forms, one of which is shown in Fig. 131. A receiving 

 tambour constructed like a drum is fastened to the chest, and is 

 connected with a recording tambour, the lever of which writes on 

 a smoked drum. The subject of the experiment should not be 

 allowed to see the movements of the lever, for the respiration is 

 easily affected by nervous impressions. Take a graphic record of 

 the respirations and mark the time relations of inspiration and 

 expiration by means of a chronograph giving seconds. Swallow 

 and note that the respiratory movement, inspiratory or expiratory 

 as the case may be, is inhibited. 



1 For other methods see Part I, p. 72. 



