204 



A MANUAL OF PHYSIOLOGY 



may be heard over a large area, the vesicular sound being 

 now suppressed, and the bronchial sound being better con- 

 ducted by the consolidated tissue than by the portions of 

 the lung that still contain air. 



Up to this point we have contented ourselves with a 

 purely qualitative description of the mechanical pheno- 

 mena of respiration. We have now to consider their 

 quantitative relations, and the methods by which these 

 have been studied. 



The expansion of the lungs in inspiration may be easily demon- 

 strated in man, and even a rough estimate of its amount obtained, 



by the clinical method of percus- 

 sion. For example, the resonant 

 note that is elicited when a finger 

 laid on the chest at a part where 

 it overlies the right lung is smartly 

 struck can be followed down until 

 it is lost in the 'liver dulness.' 

 If the lower limit of the resonant 

 area be marked on the chest-wall 

 first in full inspiration and then 

 in full expiration, the mark will 

 be lower in the former than in 

 the latter, and the difference will 

 represent the difference in the 

 vertical length of the shrunken 

 and distended lung. A similar 

 enlargement in the transverse 

 direction may be demonstrated 

 in the same way, the inner 

 borders of the lungs coming 

 nearer to the middle line in in- 

 spiration, and receding from it in 

 expiration. 



For most physiological pur- 

 poses, however, we require 



methods more delicate and more exact, and in many investigations a 

 faithful graphic record of the respiratory movements is indispensable. 

 This may be obtained : 



(i) By registering the movements of a single point, or the varia- 

 tions in a single circumference, of the boundary of the thoracic 

 cavity. In animals the end of a lever, or a small compressible bag 

 containing air and connected with a recording tambour, may be 

 placed between the lower surface of the diaphragm and the liver, 

 through an incision in the abdominal wall. In man changes in the 

 circumference of the chest at any level can be recorded by means of 

 a tambour so adjusted that in inspiration the pressure of the air in 



FIG. 77. SCHEME OF TAMBOUR 

 (BRONDGEEST'S) FOR RECORDING 

 RESPIRATORY MOVEMENTS. 



C, a metal capsule connected airtight 

 with B, A, two caoutchouc membranes, the 

 chamber formed by which can be inflated 

 by means of the tube and stopcock E. 

 The tube D connects the space H with a 

 registering tambour provided with a lever. 

 The membrane A is applied to the chest, 

 round which the inextensible strings F are 

 tied. At every expansion of the chest the 

 pressure in H is increased, and the increase 

 of pressure is transmitted to the registering 

 tambour. 



