RESPIRATION. 



267 



however, especially in women and children, is a little shorter than that 

 of expelling it, and there is commonly a very slight pause between the 

 end of expiration and the beginning of the next inspiration. The res- 

 piratory rhythm may be thus expressed : 



Inspiration . 

 Expiration 



6 



7 or 8 



A very slight pause. 



If the ear be placed in contact with the wall of the chest, or be sep- 

 arated from it only by a good conductor of sound or stethoscope, a faint 

 respiratory murmur is heard during inspiration. This sound varies 



Fig. 214. Tracing of the normal diaphragm respirations of rabbit, a, with quick movement of 

 drum, b, with slow movement, j, inspiration, K, expiration. To be read from left to right. 

 (Marckwald.) 



somewhat in different parts being loudest or coarsest in the neighbor- 

 hood of the trachea and large bronchi (tracheal and bronchial breathing), 

 and fading off into a faint sighing as the ear is placed at a distance from 

 these (vesicular breathing). It is best heard in children, and in them 

 a faint murmur is heard in expiration also. The cause of the vesicular 

 murmur has received various explanations. Most observers hold that 

 the sound is produced in the glottis and larger bronchial tubes, but that 

 it is modified in its passage to the pulmonary alveoli. In disease of 

 the lungs the vesicular murmur undergoes various modifications, for 

 a description of which one must consult text-books on physical' diag- 

 nosis. 



Respiratory Movements of the Nostrils and of the Glottis. During 



