POSIT lOX AXD SIZE OF THE HEART 155 



Rabe, it varies from 1 to 40 to 100, and taking relatively all the breeds 

 of dogs, and also of sex and age, the relative size is O.G and 2.2 to 100. 



It is difficult to make an examination of the heart on account of its 

 position, lying as it does hidden between the lobes of the lungs, with only 

 a small portion of its surface exposed where it can be heard, and from 

 the fact that it varies in size not only in the various breeds, but also in 

 individuals. We find that in animals affected with the various heart 

 affections and also in perfect health the pulmonary bruit may be so in- 

 creased that it is impossiljle to detect when there are weak heart sounds, 

 as the largest portion of the heart is covered by portions of the lungs, 

 and as these parts also make sounds the ears cannot detect the sound. 

 The restlessness of the animal during examination and the movements 

 of the cutaneous muscles and the coat of the animal are all factors that 

 assist in preventing a proper examination of the heart. 



The following details must, therefore, be looked upon to a certain 

 extent as theoretical in character. 



In making an examination of the heart we must consider the posi- 

 tion and size of that organ, its palpitation sounds, and character of the 

 23ulsations. 



Position and Size of the Heart. 



Both are to be detected by percussion, but for the reasons above 

 explained it rarely answers our expectations. In percussion over the 

 position of the heart we find in normal conditions a dull sound which 

 lessens in deep respiration. The position, either standing or recumbent, 

 may make a decided difference. 



In animals having a small heart, the sound is often entirely absent. 

 The sound of that section of the lung that lies between the heart and 

 the chest wall is also a factor that makes the sound dull, and it is only 

 by strong percussion that anj' sound can be detected at all, so that it 

 may hardly be said to be of much diagnostic value. 



There may be an abnormal dulness in the heart's action in hyper- 

 trophy, in dilatation, in exudates and transudates around the heart, and 

 in retraction or contraction of the lobules of the lung surrounding the 

 heart; but we may often be deceived by abnormal processes that surround 

 that organ, such as thickening of the lung sections or swards on the pleura. 



The dull sound is absent in enlargement of the lungs by emphysema, 

 when air has entered the pericardium, after injuries, in one-sided pleuritis, 

 and in pneumothorax. The sound is anteriorly situated in the chest 

 when there is intense metcorization of the stomach or intestines, and in 

 ascites. 



