ADVANCED EXPERIMENTAL PHYSIOLOGY 131 



something more complex than a big or mobile chest ; it involves 

 the heart which forces the blood through the lungs. Artificial 

 breathing exercises are unsound ; healthy games and sports train 

 the whole body, the component parts of which are mutually 

 dependent. 



At rest breathing is performed by healthy subjects with the mouth 

 closed, but during severe work it is opened instinctively and with 

 advantage, for there is then less resistance to the passage of the air 

 in and out of the chest, and the loss of heat is facilitated. 



The rate of respiration in healthy adult men at rest varies from 

 about 10 to 23 per minute ; men who breathe slowly take deep 

 breaths ; those who breathe quickly take shallow breaths. 



Palpation. By placing the flat of each hand upon corresponding 

 portions of the chest it is possible to compare the movements of the 

 two sides of the thorax. If the subject be told to speak, to say 

 " ninety-nine," for example, the vibration of the voice, vocal 

 fremitus, is propagated through the bronchi to the wall of the chest, 

 and thus to the hands of the examiner. 



Percussion. If a tap with the finger be given to the top of a table, 

 the note will be dull over the part directly supported by the leg, 

 but more resonant in the middle of the table. It is also easy for 

 most men to detect a difference in the sense of resistance when the 

 tap is given ; it is greater with the dull note. In a similar manner 

 the level of water in a tub can be determined. Such a method of 

 investigation of underlying structures is known as percussion. 



Firmly place the index finger of the left hand on the chest and tap 

 it with the middle finger of the other hand. Determine the differ- 

 ences in note and resistance over the various parts of the thorax. 

 On the right side the resonance extends from the apex of the lung in 

 the supra-clavicular fossa to the beginning of the dulness produced 

 by the liver under the 6th rib. On the left side it extends to the 

 cardiac dulness which begins at the 4th rib. 



Make the subject take a deep breath, and then by percussion 

 on the right side demonstrate that the limit of resonance is increased 

 owing to the expansion of the lungs. 



Auscultation. The respiratory and cardiac sounds can be heard 

 by placing the ear against the chest, or by means of a wooden or 

 binaural stethoscope. Over the trachea, or at the level of the 7th 

 cervical spine, the harsh blowing sounds, due to inspiration and 

 expiration, are heard ; these " bronchial sounds " are produced by 

 the vibration of the air at the orifices of the vocal cords and divisions 

 of the trachea and bronchi. 



Another sound, the " vesicular murmur," is heard on listening to 

 parts of the chest wall where the lung is in contact. It is a soft 

 breezy sound which increases during inspiration and dies away 

 during the first third of expiration. There are several views about 

 the causation of this sound ; it may be due to conduction of the 

 bronchial sounds. 



