In the lower third a very slight resonance may be observed over the 4th rib.; over the 5th, 6th, and 7th, where the heart approaches the surface the sound is dead; while from this to the 13th rib a slight resonance may be made out.
Right side. The upper third resembles that on left side from the shoulder as far back as the 13th rib behind which anything above the gentlest blows brings out a drum-like sound from the large intestine (double colon) especially. This is clear when that is distended with gas.
In the median third the resonance resembles that on the left side. In the lower third it equally corresponds as far as the seventh rib behind, which sound is dull because of the proximity of the liver.
Ox.—Left side. The upper third is clear in sound from the eighth to the tenth ribs, and behind this by gentle tapping to the second last (twelfth). Forcible striking, however, brings out the drum-like sound of the upper sac of the paunch which always contains more or less air.
The middle third has a clear resonance as far as the seventh rib; this diminishes to the ninth, behind which it is usually replaced by a dullness due to the presence of food in the anterior part of the paunch. By drawing back the limb percussion may be employed over the first and second ribs as well.
In the lower third the first two ribs can be examined and a clear sound should be educed. On the fourth, fifth and sixth ribs there is a full resonance, the heart being here covered by lung tissue, contrary to the condition in the horse. From the seventh the sound becomes duller and the dead sound from the food in the rumen characterizes the lower fourth of the ninth rib.
Right side. From the shoulder the resonance gradually decreases in the upper third to the eleventh rib, beyond which the sounds obtained are only from abdominal organs. In the middle third considerable resonance is met with over the first and second ribs, it is very full and clear over the fifth, sixth and seventh, whence it decreases and is quite lost behind the tenth. In the lower third a clear sound can be elicited over the first, second, fourth, fifth and sixth ribs; this is lessened over the seventh and eighth, and completely lost behind the ninth. Any but the slightest blows over these three last ribs brings out the dull, solid sound from the liver.
A very full paunch greatly increases the anterior convexity of the diaphragm, and compresses the lungs into the anterior part of the chest. If the contents of the rumen are solid the resulting dullness on percussion might be mistakenly supposed to indicate consolidation of the lung. This source of error must be carefully guarded against.
Sheep. Percussion in the sheep differs from that in the ox chiefly in the following particulars: The diaphragm being attached to the last rib as in the horse, the diminishing resonance of the lung may be traced as far back as in that animal. Thus a pulmonary sound can be obtained in the upper third as far as the last intercostal space, in the middle as far as the second last, and in the lower as far as the fourth from the last. Over the lower part of the fifth and sixth ribs on the left side the resonance is remarkably clear owing to the great relative thickness of the anterior lobe of the left lung which here covers the heart.
Pigs. In fat pigs the results are almost negative. In lean animals the middle third on each side gives out a clear resonance behind the shoulder as far as the seventh rib, from which it diminishes to the second last (thirteenth). The sound is less clear in the upper and lower thirds. On the fifth intercostal space below, and on the left side the sound is dull owing to the exposure of the heart through a slight notch in the lung.