THE SHEATH OF THE BUNDLE OF HIS 61 



towards the main branch and, in some instances, at once appeared 

 on the left side within the sheath of the left branch. Following 

 out this same idea, a complete injection of the system was 

 obtained from its point of departure from Tawara's 'Knoten' 

 to the very fine ramifying branches which lie under the endocar- 

 dium, and even to the finest terminal fasciculi which end in 

 the myocardium. The chief difficulty was to insert the needle 

 at just the proper depth to pierce the sheath. The point selected 

 for the purpose of injection was immaterial as long as the fascicu- 

 lus chosen was somewhat thicker than the needle. 



Contrary to Dogiel's view, the endocardium is always trans- 

 parent enough to permit accurate localization of the fasciculi. 

 These are readily seen as they pass along under the endocardium, 

 and after some trials few mistakes were made in inserting the 

 needle. 



Twenty-five hearts were used for the injection of the sheath 

 in this manner, eighteen of these were fresh beef hearts, and one 

 a lamb's heart, the rest being formalin-preserved hearts of cattle. 

 In all of these a practically uniform result was obtained. The 

 sheath of the atrio-ventricular bundle could be filled with the 

 colored fluids without difficulty. The lamb's heart gave an 

 especially delicate and fine picture of the injection. However, 

 as a rule, it was difficult to force the fluid upward to the main 

 bundle and farther upward to the region of the 'Knoten,' although 

 this was done in some cases. 



Fig. 1 is a photograph of beef heart no. 36 of this series, and 

 although the figure is a retouched photograph it does not repre- 

 sent adequately the extent nor the completeness of the injection. 

 This heart was opened by an incision which extended up from the 

 apex parallel to, and about three centimeters from the anterior 

 longitudinal sulcus. The view shows the left ventricle with its 

 outer wall reflected to the left. The injection mass used was a 

 suspension of India-ink. Points of injection were at 1, where 

 the left branch appears superficially and begins its downward 

 course, and at 2, where some of the ramifying divisions of the 

 left branch have come to lie upon the posterior papillary 

 muscle. The fluid, injected at 1, ran down within the sheath of 



