138 DISEASES OF THE GIRCULATOBY APPARATUS. 



down any relative rule as to its size or dimensions. According 

 to Golan, the weight of the heart compared with that of the body 

 is 1 to 90; and according to Rabe, it varies from 1 to 4 to 100, 

 and takiug relatively all the breeds of dogs, and also sex and age, 

 the relative size is 0.6 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 betweeu the lobes of the lungs, 

 and 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-afEections and also in perfect health 

 the pulmonary bruit may be so increased that it is impossible 

 to detect when there are weak heart-sounds, as the largest portion 

 of the heart is covered by portions of the lungs, and these parts 

 making sounds the ears cannot detect the sound, as the restlessness 

 of the animal during examination and the movements of the cuta- 

 neous 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 as theo- 

 retical in character to a certain extent. 



In making an examination of the heart we must consider the 

 position and size of that organ, its palpitation sounds, and char- 

 acter of the pulsations. 



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 

 where the heart lies we find in normal conditions a dull sound, 

 which lessens in deep respiration, and also the position, either 

 standing or recumbent, may make a decided difference. 



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 dull sound, and 

 it is only by strong percussion that any 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, 

 in retraction or contraction of the lobules of the lung surrounding 

 the heart; but we may often be deceived by abnormal processes 



