PEKCUSSION. 533 



regions a distinct, though moderate resonance may be 

 observed from the 1st to the 8th rib; there is no modifica- 

 tion on the left more than on the right side, over the region 

 of the heart. In all dogs in moderate condition only, percus- 

 sion may be effected over the two first ribs, which yield a 

 moderately clear sound, and over the anterior and posterior 

 fossae of the shoulder-blade, which in their turn give a slight 

 resonance, though of a much less distinct character. 

 ' Birds. In birds, over that interval between the thick pec- 

 toral muscle and the wing on each side, a clear resonance 

 is yielded on percussion. A less marked though still dis- 

 tinct resonance may be elicited by employing percussion 

 along the back in the interval between the two wings. In 

 examining these animals, it is well that the pleximeter be 

 small and thin, and that the strokes of the finger be slight. 



In states of disease the percussion sound may be aug- 

 mented, diminished, or abolished. 



Augmentation of sound may be partial or general. Partial 

 augmentation arises from an obstruction to the respiratory 

 process in the remainder of the lung tissue ; thus when one 

 lung is hepatised, its fellow, which is called upon to perform 

 its functions, must take in an increased quantity of air, and 

 hence becomes abnormally resonant. A similar result will 

 follow effusion into one or both pleural sacs; in the horse, 

 when in this condition, the resonance will be exaggerated 

 superiorly, while dulness exists lower down. General in- 

 crease of resonance is especially noticed in cases of extensive 

 emphysema. In this case the character of the sound is much 

 more clear than when there is simple exaggerated respiration 

 in a single lung. It resembles somewhat that produced by 

 percussion over the left flank in cases of hoven, and has from 

 this been designated tympanic. 



Diminution of sound may be general or partial. General 



