THE HEART 233 



which horses are liable, and most frequent of oc- 

 currence, and hence the most likely to impair his 

 usefulness. 



It is not to be wondered at, that so many horses 

 are afflicted with lung complaints, most of them re- 

 sulting from carelessness. The poor animals are too 

 often over-heated, and afterwards put into cold stables 

 in a state of profuse perspiration, and allowed to dry. 

 This should never be the case. The animal ought 

 to be instantly rubbed down, until his coat is quite 

 dry. If this is not attended to, inflammation of the 

 lungs and a host of other complaints may be the 

 consequence. 



THE HEART. 



The heart is enclosed within a membrane or bag, 

 called the pericardium, Plate ix, fig. i, c, and both 

 together occupy the middle space of the cavity of the 

 chest. The pericardium contains within it a small 

 quantity of serous fluid, which serves to lubricate the 

 contiguous surfaces of the sac, and to preserve them 

 against any ill consequences arising from friction. 



The use of the pericardium is to confine the heart 

 in its situation, to sustain it in its reciprocal action 

 with the lungs, and guarding it from any undue 

 collision, and to serve as a guard to the heart. 

 When the pericardium or the heart becomes in- 

 flamed, an undue secretion of this fluid is induced, 

 sometimes to such an extent as to obstruct the 

 beating of the heart. When such is the case, the 

 animal is said to have dropsy of the heart. 



The heart itself, fig. i, b, is the organ by which 

 the blood is circulated through the body. It is of 

 a conoid form, with the base turned uppermost, and 

 is opposed to the fourth, fifth, and sixth vertebrae 



