BLOOD-VESSELS OF THE HEART VALVES 455 



the warm l)ath surroiiiidiiig the heart was replaced with ice- 

 water. Wlieu tlie fi;(4atin had solidified in the coronary arteries, 

 the canniilae were disconnected, and the heart cut open to re- 

 move the carmin-gelatin collected in the auricles and ventricles. 

 The opened heart was then placed in 10 per cent formalin to 

 harden the gelatin in the small vessels. After 48 hours or 

 longer, the valves wvvv dissected, removing the atrio-venti'icular 

 rings with the tricuspid and mitral vah'es and strips of the pul- 

 monary artery and aorta with the semilunar valves. Vessels 

 could be seen in the upper portions of the atrio-ventricular valves 

 and sometimes in the chordae tendineae at this stage. In or- 

 der to render the whole vascular network readily visible, the 

 valves were dehyi' rated in 95 per cent alcohol, cleared in a 

 mixture of 2 parts of wintergreen and 1 part benzol. In valves 

 rendered transparent in this manner, the vessels could be studied 

 to greatest advantage with the binocular microscope. 



In the pig, the atrio-ventricular and semilunar valves and the 

 chordae tendineae are w^ell supplied with blood vessels They 

 differ only in numbers from the vessels of the valves of the 

 human heart and will not be described here in detail. 



BLOOD-VESSELS OF THE \AL\LS OF THE HUMAN HEART 



Atrio-ventricular valves 



The human hearts used for these injections were carefully 

 selected normal hearts obtained from the autopsies of the 

 Pathological Department of the Johns Hopkins Hospital. Four- 

 teen hearts were injected. These were taken from human sub- 

 jects of the following ages: 1 to 10 years, 6 hearts; 10 to 20 years, 

 2 hearts; 20 to 30 years, 2 hearts; 30 to 60 years, 4 hearts. In 

 some of these, only ii-i-egular groups of vessels and long delicate 

 arterioles extending to the line of closure of the valves were 

 shown by the injection. In three hearts fairl}^ complete injec- 

 tions were obtained. The following description is based upon 

 these injections: 



The tricuspid and mitral valves receive arterioles from the 

 annular branches of the right and left coronary arteries as these 



