RESPIRATION 



217 



like the horse and ox, dies out as an audible murmur before it 

 reaches the remotest lobules, and can only be distinguished over 

 a portion of the pulmonary area. When the glottic sound is 

 eliminated by causing an animal to breathe through a tracheal 

 fistula, the vesicular murmur is still heard, and in the horse is 

 even somewhat sharper than normal, although in the dog it is 

 softer and weaker. The expiratory murmur does not seem to 

 contain a true vesicular element, but is exclusively due to the 

 resonance of the expiratory glottic sound (Marek). It is generally 

 admitted, and this is of great importance in practical medicine, 

 that when the normal vesicular sound is heard over any portion 

 of the lung tissue, it may be inferred that this portion is being 

 properly distended, and that air 

 is freely entering its alveoli. 



Up to this point we have 

 contented ourselves with a 

 purely qualitative description 

 of the mechanical phenomena 

 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 in- 

 spiration and then in full ex- 

 piration, 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 inspiration, 

 and receding from it in expiration. The examination of the chest by 

 the Rontgen rays has also yielded results of importance in the study 

 of normal respiratory conditions, and still more important results in 

 pulmonary disease. 



For most physiological purposes, however, 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- 



FIG. 99- SCHEME OF TAMBOUR FOR 

 RECORDING RESPIRATORY MOVE- 

 MENTS. 



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 stop- 

 cock 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 inexten- 

 sible strings F are tied. At every ex- 

 pansion of the chest the pressure in H 

 is increased, and the increase of pres- 

 sure is transmitted to the registering 

 tambour. 



