304 RESPIRA TION 



and made tight with a little cotton-wool. The other nostril and the mouth 

 are closed, and respiration suspended. The column of smoke moves 

 in and out at each beat of the heart. By feeling the apex-beat, try to 

 verify the fact that during systole the cardio-pneumatic movement is 

 inspiratory, and in diastole expiratory. 



7. Auscultation of the Lungs. This is taught in the course of physical 

 diagnosis, but in connection with the subject the student may perform 

 the following experiment on a dog used for some other purpose : Open 

 the trachea as described on p. 201. 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 projecting 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 



Fig. 139. Haldane's Apparatus for measuring the Quantity of CO 2 and Aqueous 

 Vapour given off by an Animal. A, chamber into which the animal is put; 

 i and 4, Woulff's bottles filled with soda-lime to absorb carbon dioxide; 2. 3, and 

 5, Woulflt's bottles filled with pumice-stone soaked in sulphuric acid to absorb 

 watery vapour; B, glass bell-jar suspended in water, by means of which the 

 negative pressure is known; P, water-pump which sucks air through the appar- 

 atus: i and 2 are simply for absorbing the carbon dioxide and water of the 

 ingoing air. 



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. 



Repeat the observation 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 ex- 

 piraton. 



(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. 



