238 FRANKLIN P. MALL 



The remainder of the surface fibers, the sino-spiral band, arises 

 from the posterior borders of the venous ostia, converge towards 

 the apex to form the anterior horn of the vortex. In general, the 

 fibers that arise from the arterial side of the heart, the bulbus of 

 the embryo, pass to the posterior horn of the vortex, while those 

 from the venous side of the heart form the anterior horn. It may 

 be that this arrangement of the fibers is due to the bending of the 

 heart in development ; His thinks that it may be associated with 

 the formation of the inferior septum. At any rate since all of the 

 fibers that arise on one side of the heart enter the apex at the other, 

 and vice versa, their course must be spirally around the heart 

 which proves to be the case. 



To follow the bundles which arise from the septum aorticum 

 around the heart through the posterior limb of the vortex into the 

 apex and through the septum to their ends is not altogether easy. 

 This has been the great difficulty in the study of the architecture 

 of the musculature of the heart, and it will not be solved to the 

 satisfaction of all anatomists until the development of the bundles 

 is known. At present it is difficult to rest what I have found upon 

 an embryological basis for the main part of the story is run through 

 by the time the embryo is 12 to 15 mm. long, and such hearts can 

 not be dissected. Nor can the course of the muscle fibers be fol- 

 lowed with any degree of certainty through the study of serial 

 sections.'^'' 



It is apparent that the bulbo-spiral was well known to Gerdy 

 who attempted to picture it.'^^ Gerdy also observed that the walls 

 of both ventricles are formed by a series of loops which are attached 

 to the tendinous rings at the base of the heart; they become larger 

 as they extend towards the apex of the heart, and successively 

 fall into one another. The loop which reaches to the apex, the 

 bulbo-spiral, forms a double loop in passing through the septum, 

 and thereby is converted from a single loop into an 8-like figure. 

 Although Gerdy's illustrations are crude and his description is 



^^ His says, I.e., p. 177, that the fibers must develop from left to right along the 

 anterior longitudinal sulcus and from right to left along the posterior longitudi- 

 nal sulcus. 



«• Gerdy, I.e., fig. 12. 



