PERICARDITIS. 199 



The diseases of the heart and its appendages naturally 

 range themselves into three classes: those affecting the 

 pericardium ; those affecting the substance of the heart ; 

 and those affecting the lining membrane, and valves of the 

 heart and great blood-vessels. 



PERICARDITIS. 



The pericardium is by no means infrequently the seat of 

 inflammation. In opening horses that die of pleuritic 

 disease, nothing is more common than to find effusions of 

 fluid and lymph within the pericardiac cavity, as though the 

 one membrane had morbidly sympathised with the other. 

 '' Redness alone/^ Dr. Hope says, " does not aflPord coii 

 elusive evidence of pericarditis, as all serous as well as 

 mucous membranes are liable to vascular injection from 

 various causes independent of inflammation.^^ The effused 

 lymph is mostly disposed in layers upon the internal 

 surface of the sac, and upon the exterior of the heart, 

 giving additional substance to the one, and often a com- 

 plete coating to the other, and, in some instances, forming 

 adhesions between the two. In this manner, the peri- 

 cardium may be increased in thickness to an enormous 

 extent. The lymph assumes the same albuminous cha- 

 racter as it does in the chest, and, on being cut into, while 

 recent, displays a honey-comb sort of texture, having its 

 interstices loaded with a yellow serous fluid : in fact, 

 putting on the same appearance, only that it is more 

 concrete, as it does within the chest, and undergoing — 

 should it remain — the same changes towards organisation. 

 In process of time, and when it exists as an additional 

 lining to the pericardium, it grows close and firm, and 

 becomes attenuated in substance, and turns of a white 

 colour. In one instance I found it converted into a 

 substance of the nature of cartilage, about an eighth of an 

 inch in thickness. A French V.S. (Delalandc) describes a 

 strange appearance of the pericardium in a cow who died 

 of the disease. It had acquired " extraordinary size," and 



