Diseases of the Heart and Organs of Circulation. 411 



Percussion. In the horse a dull, dead sound is emitted, when 

 percussion is made over the left side, for about four inches above 

 the breast bone and in the space corresponding to the lower ends 

 and the cartilages of prolongation of the fourth, fifth and sixth 

 ribs. In the ox this dullness is less marked on the level of the 

 sixth rib. The same results can be obtained on the right side by- 

 imparting heavier blows to the chest walls, so as to derive the 

 sound from the deeper parts. 



The area of dullness is increased in cases of hypertrophy or in 

 dilatation of the heart, when the enlarged organ presses aside the 

 lung tissue and exposes a greater amount of its substance to the 

 chest walls. The same result takes place in hydropericardium. 



The area of dullness is diminished in cases of ruptured air cells 

 (as in " heaves" ) when the inflated and expanded lung tissue en- 

 velopes the heart more completely and gives out its own clear 

 resonance where the dull sound of the heart is usually obtained. 



Application of the hand. Palpation. In conditions of 

 health and in quietude the hand applied on the side of the chest, 

 close behind the left elbow only just perceives the beat of the heart 

 with each contraction. If the animal is excited, whether from 

 fear, joy or physical suffering, the heart's impulse becomes more 

 powerful and by this alone the state of its function may be very 

 satisfactorily ascertained. The impulse is strong in all active 

 fevers and extensive inflammations of important organs, but it is 

 especially marked in. diseases of the heart and lungs. Irregularity 

 in the force of successive beats is seen in various heart diseases 

 and debilitated conditions are recognized in the same way. 



Any want of harmony between the heart's action and the pulse 

 may be observed by laying the right hand over the region of the 

 heart and applying the fingers of the left on the radial artery. In 

 debility and especially if from a deficiency of blood, the violent or 

 tumultuous action of the heart contrasts strangely with the weak 

 jerking and compressible pulse. The same symptoms are noticed 

 when the valves of the heart close the orifices imperfectly. In 

 convalescence from lung diseases and in certain diseases of the 

 heart, a heart impulse may be felt by the right hand for which 

 no corresponding pulsation is felt in the radial artery by the left. 



When the heart is hj^ertrophied the impulse is stronger and is 

 associated with a full, strong, and rolling pulse. When it is atro- 



