322 RESPIRATION 



the pulmonary air very quickly strikes a balance with that of the outer air, 

 so that we meet the pressure variations just described only when the capacity 

 of the lungs is being changed by inspiratory or expiratory movements. 



In order to determine the absolute value of these pressure variations, a 

 T-shaped cannula is introduced into the trachea of a dog, the animal breathes 

 as usual through the uninjured glottis, and the variations of pressure are meas- 

 ured by a manometer connected with the unpaired limb of the cannula (Kramer). 

 This method has been used also on patients with a tracheal fistula. With nor- 

 mal persons either the manometer tube is placed in one nostril and the subject 

 breathes through the other (Donders), or he is allowed to breathe from a wide 

 bottle connected on one side with a manometer and on the other by a wide 

 tubulure with the outside air (Ewald). 



It is evident that the values obtained in these experiments must be smaller, 

 the nearer the manometer is brought to the outer openings of the respiratory 

 passages. By the last-named method Ewald found a pressure of 0.1 mm. 

 Hg. for inspiration and + 0.13 mm. for expiration. When Donders placed the 

 manometer tube in one nostril, he obtained for inspiration about 0.7 and for 

 expiration -j- 0.5 mm. Hg. In experiments on men with a tracheal fistula, Aron 

 obtained below the glottis the value of 1.9 mm. for inspiration and + 0.7 for 

 expiration. 



In order to measure the force of the different phases of respiration, a Hg. 

 manometer is placed in air-tight connection with the mouth and nose by 

 means of a closely fitting mask, and the subject breathes into the apparatus 

 (Valentin, Hutchinson). Of course no air can pass into or out of the lungs, 

 but instead the air already in them is rarefied or compressed according as 

 the effort is made to inhale or exhale. The pressure readings given by the 

 manometer may then serve as relative expressions of the power employed in 

 the two phases. By such a method Hutchinson found in ordinary breathing 

 a pressure of 50 mm. Hg. for inspiration and + ?6 mm. for expiration. 

 With the deepest possible inspiration the pressure is given at something like 

 140 to 150 mm. Hg. ; for the most intense expiratory effort possible the 

 figures vary between + 108 and + 256 mm. Hg. 



On three different individuals Mosso determined the inspiratory pressure 

 for pure costal and pure diaphragmatic breathing and found the value in the 

 former to be from 32 to 40 mm., in the latter from 10 to 20 mm. Hg. 

 (cf. page 317). 



9. THE RESPIRATORY SOUNDS 



By auscultation of the lungs and of the air passages, two different sounds 

 can be heard; namely, (1) the vesicular, and (2) the bronchial sound. 



To imitate the character of the vesicular sound one has only to suck in air 

 through the mouth with the lips pursed: a sipping sound is produced which is 

 almost exactly like the vesicular sound. It is said to be produced at the moment 

 when the air current enters the alveoli. 



During expiration there is to be heard in the normal condition of the thorax 

 a weak and soft, indefinite aspirating sound which shows no trace of the sipping, 

 vesicular sound of inspiration. 



Over the larynx one can hear during both inspiration and expiration a very 



