336 Veterinary Medicine. 



that are too small to transmit them. These sj-mptoms will be as 

 varied as the organs whose arteries are plugged. If in the brain 

 there ^may be dulness, stupor, vertigo, somnolence, delirium ; if 

 in the liver, biliary and digestive derangement ; if in the lungs, 

 cough with the other signs of pneumonia and abscess ; and if in 

 the limbs lameness and paralysis, (brought on or aggravated by 

 exercise, and often removed by a few minutes' rest), wasting of 

 the muscles, etc. (^See Embolism) . 



Causes. These are in the main the same as those of pericarditis. 

 Weak health, exposure to extremes of weather, punctures with 

 foreign bodies, but above all, the rheumatic constitution are com- 

 mon causes. Indeed rheumatism appears more prone to attack 

 the serous membrane lining the heart cavities than that envelop- 

 ing it externally. One reason for this is to be found in the great 

 and incesssantly recurring strain on the fibrous structure of the 

 valves, and particularly in hard worked horses and hunting dogs 

 in which the strain is often extreme. It has been argued that 

 the increased blood pressure caused by digitalis is an appreciable 

 cause. Its frequent coiniection with rheumatism is shown in the 

 rheumatic lesions of joints and fibrous structures seen in carcasses 

 dead of endocarditis. 



Diseases in the muscular substance of the heart as cysts, ab- 

 scess, etc., frequently extend to the endocardium. 



Among other causes must be mentioned disease-changes in 

 the blood. These may act on the valves directly as in the case of 

 lactic acid injected by Dr. Richardson, into the peritoneum with 

 the view of producing rheumatism and successfull}' as regards 

 the lesions of the cardiac valves ; or indirectly by determining 

 coagulation and irritation of the lining membrane coming into 

 contact with the clot. The very fibrinous and plastic state of the 

 blood in extensive inflammations is a probable cause of the occur- 

 rence of clots in the heart, and the frequency of such clots in the 

 dog has been ascribed to the plasticity of his blood (Leblanc). 

 The injection of pus into the blood or the absorption of microbes 

 from diseased surfaces will sometimes produce ulcerative disease 

 of the valves. The same is true as regards the germs of ompha- 

 litis, pneumonia, arthritis and other infectious diseases. 



lyafosse records certain cases of endocarditis due to extension 

 of the disease from inflamed veins. 



