554 DISEASES OF THE PERICARDIUM. 



CHAPTER XXVIII. 



DISEASES OF THE PERICARDIUM. 



I. Acute Pericarditis. 



Definition. — An active inifiammatory condition affecting the 

 fibro-serous investinfj membrane of the heart. 



Pathology, a. Causation. — Inflammation of the investing 

 and'containing membrane of the heart, although it may appear 

 as a primary or idiopathic disease, depending for its production^ 

 in acute forms, upon cold, exposure, and fatigue, is more fre- 

 quently observed as a secondary or symptomatic affection 

 developed as the result of, or in intimate association with, such 

 conditions as — (1) Certain general diseases and blood-contami- 

 nations, particularly rheumatic fever, strangles, influenza, pur- 

 pura, and many pytemic and septic conditions ; (2) From 

 extension of inflammation from contiguous structiu'es, as the 

 lungs and pleura; (3) From the irritation incident to the 

 development of new formations, as cancer, or the appearance 

 of parasitic growths ; (4) Penetrating wounds inflicted by bodies 

 from without, or by fractured ribs. 



Of all these causes or influences, probably the most potent as 

 affecting the horse are the rheumatic; while, wherever these 

 are in operation, either in the form of acute rheumatism, or of 

 epizootic catarrhal fever with a rheumatoid tendency, the 

 induced diseased action is very often complicated and accom- 

 panied with the involvement of other fibro-serous structures. 



h. Anatomical Characters. — Not only is the nature of the 

 inflammatory action which seizes on this tibro-serous structure 

 of the heart very various in the intensity of its action and the 

 symptoms which it may exhibit during its development, but 

 the structural changes which accompany, or are the result of 

 it, vary in a similar manner. Although inflammatory action 

 here may, in a general sense, be said to run a similar course to 

 that which is observed in serous membranes generally, it is yet 

 to be observed that its products and textural changes are 

 modified by the constant movement which exists between the 

 heart and its enclosing capsule. In studying these results 

 we ought i]ot merely to confine our attention to the mem- 



