DISEASES OP THE HEART. 301 



tion, or give to eacli organ that im]iulse or stimulus wliic'h enables it to 

 discharge its function, it mu^st be materially changed. 



"WTien the right ventricle contracts, and the blood is diiven into the 

 lungs, it passes over the gossamer membrane of which the lobules of the 

 lungs have been described as consisting ; these lobules being filled with 

 the air which has descended through the bronchial tubes in the act of in- 

 spiration. This delicate membrane permits some of the ])riuciples of the 

 air to permeate it. The oxygen of the atmosphere combines mth a 

 portion of the superabundant carbon of this blood, and the expired air is 

 poisoned ■with carbonic-acid gas. Some of the constituents of the blood 

 attract a portion of the oxygen of the air, and obtain their distinguishing 

 character and properties as arterial blood ; and being thus revivified, it 

 passes on over the membrane of the lobes, unites into small and then 

 larger vessels, and at length pours its full stream of arterial blood into 

 the left aui'icle, thence to ascend into the ventricle and to be diffused over 

 the frame. 



DISEASES OF THE HEART. 



It may be readily supposed that an organ so complicated is subject to 

 disease. IL is so to a fearful extent, and it sympathises with the maladies 

 of every other pai't. Until lately, however, this subject has been shamefully 

 neglected, and the writers on the veterinary art have seemed to be unaware 

 of the importance of* the organ, and the maladies to which it is exposed. 

 The OAvners of horses and the veterinary profession generally are deeply 

 indebted to Percivall in his ' Hippopathology' and to the pages of ' The 

 Veterinarian' (vol. vi.) for much valuable information on this subject. To 

 Dr. Hope also, and particularly to Laennec, we owe much. Mr. Percivall 

 well says, ' This class of diseases may be regarded as the least advance($ 

 of any in veterinary medicine — a circumstance not to be ascribed so much 

 to their comparative rarity, as to their existing undiscovered, or rather 

 being confounded duiing life with other disorders, and particularly with 

 pulmonary affections.' 



The best place to examine the beating of the heart is immediately behind 

 the elbow, on the left side. The hand applied flat against the ribs will 

 give the number of pulsations. The ear thus applied 's^dll enable the 

 practitioner better to ascertain the character of the pulsation. The 

 stethoscope affords an uncertain gaiide, for it cannot be flatly and evenly 

 applied. 



Pericarditis. — The bag, or outer investing membrane of the heart, is 

 liable to inflammation, in which the effused fluid becomes organised, and 

 deposited in layers, increasing the thickness of the pericardium, and the 

 difficulty of the expansion and contraction of the heart. The only 

 symptoms on which dependence can be placed are — a quickened and irre- 

 gular respiration ; a bounding action of the heart in an early stage of the 

 disease, but that, as the fluid increases and becomes concrete, assuming a 

 feeble and fluttering character. 



Hydrops Pericardii is the term used to designate the presence of the 

 fluid secreted in consequence of this inflammation, and varying from a pint 

 to a gallon or more. In addition to the symptoms already described, there 

 is an expression of alarm and anxiety in the countenance of the animal 

 which no other malady produces. The horse generally sinks from other 

 disease, or from constitutional irritation, before the cavity of the pericardium 

 is filled ; or if he lingers on, most dreadful palpitations and throbbings 

 accompany the advanced stage of the disease. It is seldom or never that 

 this disease exists alone, but is combined with dropsy of the chest or 

 abdomen. 



