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dissections, sheep's and calves' hearts were used. As the bundle is 

 followed up in this way, we find that we have removed the superficial 

 layer of auricular muscle and that these fine strands are proceeding 

 from the reticulum to the superficial musculature of the auricle, and 

 that they are the only connections it has with this superficial layer, 

 the fibres of which are at right angles to the bundle of His. There- 

 fore the bundle of His is not a continuation of this layer. 



The reticulum begins on the auricular side of the central cartilage 

 where it spreads out immediately, having an area of about a square 

 centrimetre. It is similar in color to the auriculo-ventricular bundle 

 and is not so hard as the ordinary auricular or ventricular muscle. 

 In my dissections it is flat and has a surprisingly uniform shape, some- 

 what like that of a nerve ganglion. It has a very thin capsule of 

 connective tissue, which is a continuation of the sheath which sur- 

 rounds the bundle, but it is thinner and more delicate. If in dissection 

 we get outside of this sheath, it will be impossible to reveal the reti- 

 culum as a definite structure, but if we dissect carefully, not having 

 the specimen too wet, and follow the sheath which is the natural line 

 of cleavage, a dissection can be made similar to the plates shown. 

 When the reticulum is dissected out, as in Fig. 3, we find that there 

 are several well-marked bands which can be traced for a short 

 distance into the auricles, as well as many more minute twigs — all 

 arising in this reticular mass. As these bands leave the reticulum, 

 they are distinctly pale in color like the other part of the system, 

 but they gradually merge into the ordinary auricular musculature. 

 Each part of both auricles would seem to be connected with the re- 

 ticulum through these bands and through smaller twigs. The largest 

 three are shown in the photograph of the dissection of the calf's 

 heart, Fig. 3. The small twigs which went to the surrounding muscle 

 close by have been dissected away, leaving three large auricular connec- 

 tions and the main bundle going to the ventricles, and also a well- 

 marked bundle which enters and disappears into the ventricular muscle 

 just before the main bundle leaves the auricle through the central 

 fibrous cartilage. Some of the fibres of this bundle end in the septal 

 cusp, and some pass through under the susp into the mass of muscle 

 which arises from the central fibrous body. This part of the bundle 

 (going to the ventricle under the cusps) has not been described before, 

 unless it may be the second muscular connection mentioned by Kent, 

 in which he described a spindle-celled connection as well as the con- 

 nection now known as the bundle of His uniting the auricle to the 

 ventricle, to be found in the auriculo-ventricular fibrous ring. Doubt- 



