Endocarditis. 463 



that have already formed colonies in some other part of the body. 

 Very frequently in animals, as in man, the invasion of the serosa 

 covering the fibrous valves is but an invasion by the germs of 

 rheumatism which have been already colonized in joints, fascia, 

 tendons or other fibrous structures in other parts of the body. 

 That it should concentrate its assault on the auriculo-ventricular 

 and arterial valves, is doubtless explained by the stronger blood 

 tension operating on these than on other valves in the circulatory 

 system, — in the veins, for example, and the lymphatics. This 

 view is corroborated by the fact that the valves on the left side 

 of the heart, that are subjected to the greatest blood tension, are 

 the most subject to attack in extra-uterine life, while the right 

 side which contracts less powerfully, causing less tension, is less 

 often affected. This is the more remarkable in view of the fact, 

 that the right side is by far the more frequently affected with 

 dilatation, the weaker walls being unable to compress the blood 

 as forcibly, and their readiness to yield to pressure further re- 

 straining the strain that might be thrown on the valves. The 

 notorious influence of cold (rain, sleet, snow, wading or swim- 

 ming in cold water, cold draughts, etc.) in laying the system 

 open to rheumatism is equally operative in predisposing the 

 cardiac valves to the specific rheumatic attack. As in articular 

 rheumatism, too, a traumatic or mechanical lesion of a joint will 

 predispose it to rheumatism (the essential microbian cause being 

 present) so, in the cardiac valves, their strain or injury lays 

 them more open to attack. 



Again, morbid conditions of the circulating fluids, modifying 

 the nutrition and other conditions of the tissues, tend to predis- 

 pose these (valves) to colonization by the microbes (of rheu- 

 matism, etc.) that may be present. 



But, although endocarditis is very often rheumatic, in a debili- 

 tated condition of the valves, it may be the result of almost any 

 microbian infection then present and generally diffused through 

 the blood. In the horse, it is especially found in connection 

 with omphalitis, pneumonia, pleurisy, influenza, arthritis, abscess, 

 pyaemia, osteomyelitis, etc. The larva of the sclerostoma equi- 

 num is an occasional cause. In cattle, aside from the common 

 rheumatic factor, it is especially connected with tuberculosis, 

 omphalitis, arthritis, bone disease, pleuro-pneumonia, pyaemia. 



