292 A MANUAL OF PHYSIOLOGY 



(b) Bronchial Breathing. Place the stethoscope over the trachea, 

 where the breath-sounds are of the bronchial type, although louder 

 than the bronchial breathing heard over a consolidated area of lung 

 in pneumonia. The expiratory sound is generally louder than the 

 inspiratory, and at least as long as the inspiratory sound, extending 

 throughout the greater part of expiration. Both sounds are higher 

 in pitch than the vesicular murmur, and have a blowing character. 

 Go over the chest, and note the points at which bronchial breathing 

 can be heard. 



(c) Repeat (a) and (b), using the ear applied to a towel laid over 

 the various regions of the chest instead of the stethoscope. 



(d) Perform the following experiment on a dog used for some 

 other purpose : Open the trachea as described on p. 186. Insert 

 into it the cross-piece of a glass T-tube of as large a bore as possible, 

 tying the trachea over it on each side of the stem. The stem pro- 

 jecting from the wound is armed with a short piece of rubber tubing, 

 which can be closed at will with a clip. When the tube is thus closed 

 the animal breathes through the glottis in the ordinary way. When 

 the tube is open, and the mouth and nose covered tightly with a 

 cloth, no air goes through the glottis. The tube being closed, listen 

 with the stethoscope or the ear alone over a part of the chest where 

 the vesicular murmur is well heard. If the rubbing of the hairs 

 below the stethoscope causes disturbing sounds, shave a portion of 

 the skin. Continue listening while an assistant closes the tube and 

 covers up the animal's muzzle. Determine whether any change 

 takes place in the vesicular sound. 



(e) Repeat (d) while listening over the lower part of the trachea, 

 and determine whether any change takes place in the bronchial 

 breathing sound. &*& 



8. Respiratory Pressure. Connect a strong rubber tube with a 

 glass bulb, and the bulb with a mercurial manometer provided with a 

 scale, (i) Fasten the tube with a little cotton-wool in one nostril, 

 breathe through the other with closed mouth, and observe the 

 amount by which the level of the mercury is altered in ordinary 

 inspiration and expiration. 



(2) Repeat the observation with forced breathing, pinching the 

 tube at the height of inspiration and expiration, and reading off the 

 maximum inspiratory and expiratory pressure. 



(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. Determination of Carbon Dioxide and Oxygen in inspired and 

 expired Air (i) Estimation of Carbon Dioxide. Fill a burette with 

 water, and close the pinchcock on the rubber tube. Immerse the 

 wide end of the burette in a large vessel of water, and fill it with 

 carbon dioxide by putting into it below the water a tube connected 

 with a bottle in which carbon dioxide is being evolved by the action 

 of hydrochloric acid on marble chips. See that gas has been coming 

 off freely from the bottle for a little time before the tube is put under 

 the burette. Do not fill the burette with gas beyond the graduated 

 part. To prevent warming the burette by the hand, hold it, by 

 means of a clamp or test-tube holder, in the vertical position, its 

 mouth being still immersed. Make the level of the water the same 

 inside and outside, and read off the meniscus. Then introduce a 

 piece of stick sodium hydroxide, close the burette with a finger or the 

 palm of the hand, lift it out of the water, and by a sort of see-saw 



