82 CLINICAL DIAGNOSTICS. 



ribs it comes in immediate contact with the thoracic wall. (See 

 Fig. 26.) 



Dog. The heart is of rounder form and lies very obliquely, 

 touching the chest wall along a narrow strip from the 4th to the 

 7th ribs. The apex is below the 6th intercostal space. (See 

 Fig. 27.) 



Palpation of the heart's region. The beat of the heart can 

 be felt by laying the flat of the hand over the cardiac region. 

 Inasmuch as the anconeus muscles partly cover the region, the 

 hand should be placed between them and the chest wall. In 

 the depths a dull thud will be felt, produced by the thumping 

 of the heart against the chest wall. The beat is due to a con- 

 traction of the heart's muscles which causes a slight torsion of 

 the organ to the left, bringing the left side, not the apex, 

 in contact with the wall of the chest. The beat can best be felt 

 in all animals just at the 5th intercostal space at the union of 

 the ribs to the cartilages of the sternum. The force with which 

 the beat can be felt depends upon the condition of the animal 

 as to flesh, it being more plainl)' marked in thin animals, and 

 just after severe exercise or excitement. Only in the dog can 

 the heart's beat be felt normally on the right side. 



The force of the heart's beat can be increased 

 or diminished. When the force of the beat is much increased 

 a palpitation of the heart is spoken of. It occurs : 



1. In hypertrophy of the heart (here combined with 

 strong pulse). 



2. In heart's weakness, the muscles of the organ un- 

 dergoing spasm-like contractions incapable of properly pro- 

 pelling the blood to the periphery, the pulse being small. The ■ 

 condition is seen in acute myocarditis, endocarditis and peri- 

 carditis. 



3. Where the lung between the heart and the chest wall 

 becomes thickened. 



The heart's beat is weakened: 



1. Where the force is enfeebled from degeneration of 

 the heart's muscle. 



2. Where the heart is crowded away from the chest 

 wall by accumulations of exudate in the thoracic cavity 

 (pleuritis, pericarditis), or in some cases of pulmonary em- 

 physema or tumors. 



Percussion of the heart. Except in very thin animals 

 (horses) the percussion of the heart is of no great value in 



