THE A URICUL O- VENTRICULAR VAL VES. 



Fig. 4. 



-Mitral valve. Insertion of the chords 

 tendinere. — Krehl. 



Fredericq 1 and Porter, 2 by more delicate methods of investigation, 

 have obtained distinct signs of a slight rise in auricular pressure, which 

 occurs synchronously with the upstroke of the ventricular pressure 

 curve, but this is probably not caused by the regurgitation of blood, but 

 by the ballooning out of the 

 auriculo-ventricular valve. 

 By plugging the pul- 

 monary orifice with wax, 

 and then directing into 

 the ventricle a stream of 

 water from the height of 

 one foot, Baumgarten 3 ob- 

 served that the auriculo- 

 ventricular valves closed 

 firmly immediately after 

 the cessation of the stream. 

 This results from the pres- 

 sure exerted on the fluid 

 in the cavity by the elastic 

 rebound of the muscular 

 walls. The result of such 

 an experiment cannot be 

 directly applied as an explanation of the closure of the auriculo- 

 ventricular valves in the living heart, for the filling pressure in the 

 auricle is often extremely slight, and can give origin to but little elastic 

 rebound. 



As the blood presses equally on either side of the margins of the 



valves when placed in apposition, these 

 need no great strength, and are in fact ex- 

 ceedingly delicate. The remainder of the 

 valve, on the other hand, bears the full strain 

 of the pressure, and, consequently, is much 

 tougher. The chordae tendineee are affixed 

 both to the ventricular surfaces and close 

 to the free edges of the valve flaps. Each 

 flap is supplied with cords from two papil- 

 lary muscles, and these are situated oppo- 

 site to each other. The resultant pull of 

 the cords is shown by the direction of the 

 arrow in Fig. 2. 4 



By the insertion of a finger into the 

 heart of a living horse, Chauveau and 

 Faivre 5 determined that an elevation of 

 the auriculo-ventricular valves can be felt 

 to take place before the flaps come absolutely into apposition. When 

 closed, the valvular diaphragm appears slightly ballooned out towards 



Fig. 5. — Diagram of the ehordre 

 tendinerti. — Krehl. 



1 "Trav. du labor, de Liege," 1888, tome ii. p. 116. 



2 Porter, Journ. Physiol., Cambridge and London, 1892, vol. xiii. p. ;V24. (T. Gottwalt, 

 Arch. f. d. gcs. Phijsiol., Bonn, 1881, Bd. xxv. S. 1; Riegel, Deutsche* Arch. f. Min. 

 Med., Leipzig, 1862, S. 1 and 471. 



3 Arch. f. Anat., Physiol, u. wisscmch. Med., Berlin, 1843, S. 463. This experiment 

 was originally performed by Lower. 



4 Ludwig, "Lehrbueh der Physiologie," 1861, Bd. ii. S. 81. 

 5 Gaz. vied, de Paris, 1856, p. 410. 



