280 CIRCULATORY APPARATUS. 



inflammatory irritants upon the endocardium. According to 

 Bamhergers estimate, 20 ^/o of ali the cases of acute articular 

 rheumatism are complicated Avith endocarditis. 



As regards the more precise localisation of the process, we 

 must first call attention to the fact, that the endocardial lining 

 of the left heart is so preeminently liable to become affected that 

 cases of endocarditis of the right heart belong to the curiosities 

 of pathology. Next, there is a marked connexion between the 

 seat of the disease and the mechanical irritation to which certain 

 regions of the endocardial surface are exposed during the heart's 

 contractions. Such are the lines along wliich the valve-flaps 

 come into contact during their closure ; not the free edges of the 

 valves, but lines which even in the normal state are very appa- 

 rent on the sigmoid valves, lines which coincide with the free 

 border of each flap only at its middle point (nodulus Arantii) 

 and at its two extremities, but which are separated from it else- 

 where by an interval of from half a line to one line ; on the cuspid 

 valves the "line of contact" is everywhere one line off the free 

 border ; it runs along the upper surface of each flap, correspond- 

 ing exactly to the insertion of the upper ends of the forked 

 chordge tendineas upon its inferior or ventricular aspect. It is 

 here as a rule that we nmst seek for the earliest signs of morbid 

 change. Starting from hence, the mischief may extend over a 

 great part of the valve ; it may burst forth simultaneously at 

 another point of the endocardial surface ; but the "lines of con- 

 tact " of the valves are and continue to be its favourite seat. 



§ 250. The textural change in acute endocarditis is made 

 up of three factors of very unequal Aalue. In the first place, an 

 implication of the vasa vasorum may be demonstrated wherever 

 they happen to run in the neighbourhood of the inflamed part. 

 Congestion and a considerable proliferation of the corpuscular 

 elements of the adventitia may always be shown in trans- 

 vei'se sections through the inflamed curtains of the mitral valve 

 (fig. 87, &). Of far greater moment are the progressive changes 

 which take place in the non-vascular, most superficial lamellag 

 of the endocardium. Their connective tissue, owing to the pro- 

 liferation of young cells in large numbers and a simultaneous 

 softening of the intercellular substance, swells up to such an 

 extent, that even with the naked eye we can detect a series of 

 warty prominences on the surface of the valve (fig. 87, c). 



