240 FRANKLIN P. MALL 



by no means clear, it is evident, that he recognized the main 

 groups of muscle bundles of the heart, for he studied the muscle 

 bundles of the whole heart, including those of the septum. 



The long muscle bundles around the left ventricle, those form- 

 ing the figure 8 according to Gerdy, were better described and 

 illustrated by Ludwig in his well-known study. However, 

 Ludwig's figure 8 is not open above like Gerdy's, who con- 

 nected one limb of the double loop with the tendinous structures 

 at the base of the left ventricle and the other to the base of the 

 right. According to Ludwig," the loops forming a figure 8 are 

 confined to one ventricle. The course of the fibers which arise 

 externally at the base of the ventricle encircles the apex and returns 

 on the inside of the heart to be attached at the base again. Those 

 that arise deeper encircle the heart midway between the apex and 

 the base and end again at the base; they form a complete figure 8. 

 In general, I find this description of the main muscle bundles 

 of the walls of the ventricles the most nearly correct, although his 

 schema is not accepted by Krehl.^"* In Krehl's publication a 

 band of muscle is described which is not attached to the tendinous 

 structure at the base of the heart, but instead makes a complete 

 circle and ends in itself. That this cannot be correct is evident 

 from Krehl's own description''^ when he says that the direction of 

 the course of the fibers of this layer is practically the same as the 

 rest of the fibers of the wall of the ventricle. In the circular layers 

 (Triebwerk) the fibers on the outside run from above downward 

 from left to right and on the inside in the opposite direction. While 

 many may see in Krehl's description a contradiction to Ludwig's 

 original description, I see in it only a confirmation. Where Krehl 

 erred was in saying that the fibers in his circular layer do not arise 

 nor end in tendons as do the outer and inner muscle layers of 

 the heart. Since MacCallum succeeded in unrolling the wall of 

 the left ventricle into a single sheet of muscle showing that it 

 must form a scroll, it has been difficult for us to account for Krehl's 

 statement regarding a middle muscle band in the wall of the left 



" Ludwig, I.e., fig. 8. 



68 The work of Krehl was done in Ludwig's laboratory and received his approval. 



"9 Krehl, I.e., pp. 347, 349, and figs. 9, 10. 



