520 AUSCULTATION. 



or pleuritic effusion, which can only be overcome by the whole 

 force of inspired air. In some such cases the obstruction 

 may be removed by coughing the animal. On other occa- 

 sions, as in spasmodic asthma, the murmur, though evident 

 at the commencement, is lost towards the end of the act. 

 Still another modification is that in which the respiratory act 

 is interrupted, and seems to proceed by a number of succes- 

 sive jerks. This is common in pleurisy, when the lancinating 

 pain prevents the subject taking a full continuous inspira- 

 tion. 



Complete absence of the vesicular sound may claim different 

 sources. It may result from hepatisation, in which case it 

 has been preceded, and in case of recovery will be followed, 

 by a crepitant rale. If dependent on that variety called 

 splenisation, no crepitant rale will have preceded its onset; it 

 is generally accompanied by a, tubal sound. Effusion into 

 the cavity of the pleura is not an infrequent cause, one or 

 both lungs, according to circumstances, being compressed by 

 the fluid. Such cases are generally ushered in by friction 

 sounds, and always exhibit the dulness on the lower part of 

 the thorax. By turning the smaller patients upon their 

 backs, such cases can thus afford the most satisfactory evidence 

 of their character. These two are the most common sources 

 of this symptom. Others, however, exist as tumours pressing 

 on one or more large bronchial tubes, considerable tubercu- 

 lous deposition, or the occlusion of bronchial tubes by blood, 

 pus, mucus, or fibrinous exudation. 



The bronchial sound is likewise liable to great variations. 

 Its most common modification, perhaps, is its presence at 

 parts of the chest in which it is not normally heard, and in 

 this case unaccompanied by the vesicular murmur. This is 

 called bronchial respiration, and is nearly constantly present 

 in cases in which the pulmonary tissue has become hepatised 



