Auscultation. 165 



the two layers may rub on each other and produce distracting 

 sounds. In mediate auscultation . the instrument should be held 

 perpendicularly to the surface, accurately applied alike to the 

 skin and the ear, and pressed firmly on the surface to condense 

 the soft structures beneath the skin and render them more con- 

 ducting. If held by the hand care must be taken to avoid the 

 slightest movement of the fingers on the stethoscope, and long 

 hairs should be prevented from entering the tube as being likely 

 to produce additional sounds. 



Among other points the following must be attended to in aus- 

 cultation. Avoid a position in which the animal can strike you 

 with its hind limbs. If necessary in irritable or ticklish subjects 

 have one fore leg held up. Select a quiet time and place, early 

 morning or night is usually best. Endeavor to protect the pa- 

 tient from the irritation of insects or the examinations may be 

 fruitless. Never auscultate over a contracting muscle ; the sound 

 of muscular contraction will prevent a correct result. If the 

 natural sounds are indistinct increase them by exercise. The 

 smaller animals are examined with the greatest facility standing 

 upon a table or held in the upright posture with the body resting 

 on the thighs or on the hind feet only. Birds can be held by the 

 wings which may be raised and drawn inward towards the median 

 line to expose the back and sides of the chest. 



HEALTHY CHEST SOUNDS. 



In all healthy animals two distinct sounds are heard over the 

 chest : — ^tlie tubal or bronchial sound, and the vesicular or 

 respiratory murmur. The bronchial sound caused by the air 

 sucking through the larger bronchi is best heard by applying the 

 ear to the breast over the lower end of the windpipe or to the upper 

 third of the chest immediately behind the shoulder. The respira- 

 tory murmur is clear and full in the middle third of the chest im- 

 mediately behind the shoulder. It is louder and more prolonged 

 in inspiration than in expiration and in the right lung than the 

 left especially in cattle and sheep in which the former is more 

 capacious. It is louder in young animals than in old, hence the 

 name of juvenile respiration applied by I^eblanc. In thin animals 

 it is better heard than in fat ones, the chest walls being thinner, 

 firmer, and more conducting. In animals of a nervous tempera- 



