92 



less the functioo of these fibres is to supply the posterior part of 

 the septum and the adjacent ventricular muscle. It is indeed what 

 one would expect to find, seeing that there is no backward turn- 

 ing branch from the main bundle of His which would supply a large 

 part of the posterior musculature. This branch is well marked and 

 easily dissected in the sheep's and calves' hearts and can, with some- 

 what more careful dissection, be made out in the human heart. I 

 have no doubt it is always present, even if at times it is less marked. 

 This would explain the experiments of Paukel, in which he ligatured 

 the main bundle and still had no incoordination in the beat of auricle 

 with ventricle. The coordinating impulses may have been conducted 

 through this branch. 



The auricular connections in the sheep's and calves' hearts consist 

 chiefly of three large bands radiating out from the reticulum viz: 

 — 1) a branch to the interauricular septum and proceeding almost 

 as far as the superior cava where it is lost in the auricular muscu- 

 lature; 2) a branch, as shown in Fig. 3, which can be traced to the 

 pericardial surface of the right auricle, blending with the auricular 

 muscle as it proceeds on its way to the pectinate muscles of the right 

 auricular appendix ; 3) a similar branch going to the left auricle which 

 can be seen as in Fig, 3 where it gives some branches to the coro- 

 nary sinus. Besides these; there are numerous smaller branches radi- 

 ating from the reticulum to adjacent auricular muscle. These are fine 

 threads of muscle and can be well seen in the human heart, in which 

 the above mentioned main branches are not so well marked. The 

 smaller radiations are also of a paler kind than the ordinary auricular 

 musculature. The auricular connections are not so easily dissected 

 as the ventricular bundles, owing to there being no bursal space ; and 

 the sheath of at all existing distal to the reticulum is not so marked. 

 But the color of the muscle helps us greatly in the dissection, and 

 when we are familiar with its relationship we cannot but be im- 

 pressed with its morphological difference from the rest of the auricular 

 muscle. This difi"erence of color has been pointed out in the ventricular 

 portions, where it is very striking; but its arrangement as well as 

 its color are almost quite as noticable in the auricular connections. 

 The reticulum has the naked eye appearance of a nerve ganglion, 

 and streaming from it or to it are certain well defined bundles of 

 muscle. For descriptive purposes in this paper I have called these 

 bundles branches of the reticulum. If the reticulum were a fixed body 

 as a cartilage or the fibrous ring, we might be inclined to call it the 

 insertion of these bands; but it is quite moveable — more so than 



