90 



things which enables us to distinguish the auricolo-ventricular system 

 from the surrounding muscle. Occasionally there is an excess of fluid 

 in hearts with endocarditis, and one may be able to demonstrate the 

 bursa by pressing the tissue on either side and watching through the 

 endocardium for a movement of the fluid. There are several forms 

 of bursa, ranging from well lubricated loose areolar tissue to distinct 

 cavities filled with lubricating fluid. These larger spaces are con- 

 tinuous with the cellular tissue around the ramifications of the bran- 

 ches of the auriculo-ventricular bundle. Out of 96 fresh human hearts dis- 

 sected, the essentials of a bursa were always present. When the bundle 

 lies along the lower border of the pars membranacea septi, and the 

 chordae from the valves are inserted just over it, the bursa is well 

 marked. This is the usual position of the bundle. When the septal 

 musculature invades the pars membranacea septi, as in Figs. 1 and 

 2, it is also well marked. These figures show the bursa as it is in 

 such cases. The drawings are from the same heart. It will be noticed 

 that in this variation which is quite common in human hearts the 

 main bundle is pushed to the left side of the septum, and the bursa 

 can be demonstrated both here, as shown by the thread holding it 

 out, and from the right side just before it disappears behind the nodule 

 of muscle to go to the left side. It will be remembered that the left 

 septal branch of the auriculo-ventricular bundle lies immediately under 

 the endocardium in the left ventricle. To show that the loose tissue 

 about this is continuous with the bursa, one may insert a blow pipe 

 into the main bursa from either side of the heart and blow it up with 

 air and the bubbles can be seen along the course of the left septal 

 branch. 



The Auricular Connections of the Bundle. 



A great deal of work has been done on the ventricular connec- 

 tions of the bundle of His, but little information is to be found con- 

 cerning the auricular side. Strangely enough the writers seemed to 

 be content with the statement that it has its root in the annular and 

 septal fibres of the right auricle. This is the most I have been 

 able to find in the literature concerning the auricular connections. 



In my dissections I tried to trace the system to its ultimate 

 ending in the auricles by following the main bundle through the cen- 

 tral fibrous body or cartilage, keeping on the surface of it until I 

 could dissect no further without cutting small strands of muscular 

 tissue, which come from the meshwork from which the bundle has been 

 described to arise, and which Keith calls the reticulum. In the first 



