EXAMINATION 71 



2. The Heart.— This is best examined in small animals, by 

 («) palpation, (b) percussion, and (c) auscultation. 



(a) Palpation. The heart beat is readily felt in all small 

 animals by placing the hand over the cardiac region (between 

 the fourth and seventh ribs, lower third of thorax on either 

 side). The heart beat can be felt on both sides of the chest. 

 This method of determining the frequency of the heart beat 

 is practical especially in very young or small animals, and, 

 as noted, also gives us the frequency of the pulse. 



The force of the heart beat depends largely upon the con- 

 dition of the animal (emaciated or fat), and whether taken 

 during exercise, excitement or at rest. 



The force of the heart beat is increased in the following 

 conditions : 



In hypertrophy of the heart, acute myocarditis, endo- 

 carditis, and pericarditis; some poisons, such as aconite and 

 digitalis; after severe exertion or excitement; after consider- 

 able loss of blood; where the temperature is elevated. The 

 heart beat is weakened in the following : Degeneration of the 

 heart muscle; the later stages of acute infectious diseases; 

 some poisonings; compression of the heart in hydrothorax, 

 hydropericardium, pneumopericardium; emphysema of the 

 lungs, and in the effusion stage of pleuritis. In unilateral 

 pleuritis the normal force of the beat may be more plainly 

 noted on the healthy than on the diseased side. 



(b) Percussion. This is of little value in diagnosis in 

 small animals. The zone of cardiac dulness is between the 

 fourth and seventh ribs. This zone is normally about two 

 to two and one-half inches in diameter. 



The zone of cardiac dulness is increased in hypertrophy 

 of the heart; hydropericardium; tumors and induration of 

 the lungs (chronic interstitial pneumonia). The zone is 

 decreased in emphysema of the lungs and pneumothorax. 

 Pain is observed on percussion in acute pericarditis and myo- 

 carditis. 



(c) Auscultation. This method of examination is of great 

 value in determining the condition of the heart. It is best 

 done in the small animal by placing the patient in a standing 

 position on a table, covering the cardiac region with a cloth, 



