THE DISEASES OF ANIMALS. 217 



Situation. — The heart lies in the region occupied by the 

 fourth, fifth, and sixth dorsal vertebras, right in the central 

 region known as the cavity of the chest. Its apex is inclined to 

 the left side. 



It appears that in the ox, the heart differs in construction 

 from that of the horse, in the following peculiarities. There is 

 a bone found in the heart, termed, os cordis, the function of 

 which has never been explained ; yet it is evidently intended 

 for some useful purpose, perhaps to give strength and durability 

 to the sanguinous force-pump. Next we notice some difference 

 in the internal mechanism of the right ventricle; there are 

 several fleshy bands running across from side to side which 

 prevents abnormal dilatation, for taken as a whole, the venous 

 system of the bovine species is more developed than in the 

 horse, the veins are larger and more numerous, and more blood 

 is constantly accumulating in the right auricle and ventricle — 

 hence the need of additional muscular mechanism. 



THE HEARTS FUNCTION. 



The blood having gone the rounds of the circulation, enters 

 the anterior or right cavity — auricle — it then passes into the 

 venous or right ventricle ; by the contraction of this ventricle 

 the blood is forced through the pulmonary arteries into the lungs, 

 there having undergone certain changes (which have been al- 

 luded to in another part of this work), it returns by the pulmo- 

 nary veins to the left auricle, from thence it descends into the 

 left ventricle. The contractions of the left ventricle force the 

 blood into the great aorta — anterior and posterior — which 

 gives rise to a numerous set of arteries, through which chan- 

 nels the blood reaches the extreme parts of the system. 



DISEASES OF THE HEART. 



Diseases of the heart in cattle are very common, yet they 



frequently elude detection simply because the symptoms are 



very obscure. Mr. Gamgee contends that the most common 



cause of diseases of the heart in cattle, is the passage of needles 



19 



