AUSCULTATION. 509 



thereby preventing the dilatation of the thorax. The species 

 of animal influences. Thus the horse, goat, dog, pig, and 

 birds present an intense respiratory murmur; in sheep it is 

 perceptibly diminished, while in the ox, cceteris paribus, the 

 sound is very distinctly less. Lastly, in young animals this 

 murmur is decidedly stronger than in adults, and is known 

 as puerile, or in the case of the lower animals, juvenile 

 respiration (LEBLANC). This peculiarity in young animals 

 would seem to depend on the smaller size of the air sacs, 

 and the greater elasticity of the lung substance. In very 

 old subjects it becomes very weak, and is known as senile. 

 Independently of these sources of difference, considerable 

 modification may be met without any apparent cause. 

 In such cases, the two sides of the chest in the same 

 region ought to be compared, or two parts on the same 

 side, which normally present the same indications, and if 

 these do not correspond, an abnormal condition is to be 

 inferred. 



The term bronchial or tubal sound were perhaps more 

 properly applied to that heard on laying the ear over the lower 

 end of the trachea, in front of the thorax. This sound has been 

 already referred to as the trachea-bronchial. The term bron- 

 chial is applied to the healthy sound perceived immediately 

 behind the shoulder in the superior region of the chest. It is a 

 somewhat harsh blowing sound, dependent on the column of 

 air striking against the walls of the bronchial tubes in its 

 course to and from the air cells, with some superadded respira- 

 tory murmur from a small intervening portion of lung tissue. 

 The bronchial sound, so far at least as its blowing noise is 

 concerned, differs from the vesicular in being almost as intense 

 and prolonged in expiration as in inspiration. It likewise 

 differs in having a distinct interval between the inspiratory 

 and expiratory sounds, dependent, no doubt, on the time 



