THE RESPIRATORY SYSTEM. 381 
Pe LS ANS] eS va.e PNY 
Wales ia Lette LR KAI Doan ened \! Wn 
FINRA NAGATA AION VASA ia C/U 
TY i ranicely Roel Na V i 
\ NUE] MUNA ANY 
NN WAY ANI UM 
Pee TPL ET Wines Lao 
Gian and reer an ry I 
4 
Fia. 314.—Tracings of respiration of horse when at rest and after exercise (after Thanhoffer). 
J, inspiration ; E, expiration. Spaces between vertical lines indicate time periods of one 
second each. 1, animal standing at rest; 3, after walk of few minutes; 7 and 8, after 
trotting ; 9, after a brief rest ; 11, after trotting and running for some minutes ; 17, after 
resting from last for a short time ; 51, tracing at end of experiment. 
Respiratory Sounds.—The entrance and exit of air are accom- 
panied by certain sounds, which vary with each part of the 
respiratory tract. To these sounds names have been given, but 
as they are somewhat inconstant in their application, or at least 
have several synonyms, we pass them by, recommending the 
student to actually learn the nature of the respiratory murmurs 
by listening to the normal chest in both man and the lower ani- 
mals. With the use of a double stethoscope he may practice upon 
himself, though not so advantageously as in the case of the heart. 
The sounds are caused in part by the friction of the air, 
though they are probably complex, several factors entering into 
their causation. , 
COMPARISON OF THE INSPIRED AND EXPIRED AIR. 
The changes that take place in the air respired may be 
briefly stated as follows: : 
