ACUTE PERICARDITIS. 555 



brane, or the fluid, or other products found in the cavity, but 

 we ought to take into consideration the state of the tissues 

 in contiguity with these. The diseased action once started 

 may, in a comparatively short period, subside, and the textures 

 return to their normal condition. Usually, however, following 

 the hypertemic state, a considerable quantity of both serous 

 fluid and lymph are poured out, and are found in varying pro- 

 portions in connection with the membrane and the sac which 

 it goes to form. The quantity may be trifling in amount, and 

 may be readily absorbed ; it may be considerable, and by its 

 mechanical presence act adversely on the functional power of 

 the heart, and may even tend to impair the integrity of its 

 muscular fibres. Very often accompanying this fluid there is 

 a greater or less amount of lymph of varying character and 

 consistence, which may sometimes exist in greater amount than 

 the more watery elements of the exudation. At other times the 

 power and capacity for organization of this plastic material is 

 greater, or the amount of fluid being less, the surfaces, visceral 

 and parietal, become coated with an adhesive material, by 

 which they become glued together, and these adhesions of a 

 more or less perfect character are extensively distributed over 

 the membrane intermingling with the contained fluid. The 

 tendency to exudation of a plastic but only moderately-well 

 fibrillated material is very gTcat in pericarditis ; so much so, 

 that in all animals a very frequent form which this assumes is 

 that of being completely spread over the heart's surface, but 

 only forming a very loose attachment to the pericardial sac. 

 When distributed in this manner it invariably assumes a 

 reticulated or honeycomb appearance, extremely characteristic, 

 and of considerable thickness, though, as already stated, of not 

 much tenacity, and easily detached from the pericardium. 



Occasionally pus is mingled with the inflammatory products, 

 or they are stained with blood, evidently from the newly- 

 formed vessels in the friable exudate, which have given way, 

 or from the congested and inflamed capillaries of the primarily 

 involved serous membrane. 



In the acute rheumatic and epizootic cases of pericarditis 

 the muscular tissue of the heart, together with the endo- 

 cardial membrane and valves, are involved to a greater or less 

 extent. The muscular tissue seems to undergo a change both 



