2G6 FRANKLIN P. MALL 



sections su])])oit Boicllis cunception of the lucchaiiisin of the heart 

 beat. In order to make it clear to the reader two illustrations 

 of the same heart, in diastole and in systole, are given. The 

 curved arrows in figs. 19 and 20 indicate the necessary rotation 

 of the heart at its apex to convert the one figure into the other. 

 It is to be noted that this specimen is from a i^ig's heart in which 

 the circular band at the base is much more pronounced and that 

 of the septum much less marked than in man. Also the ending 

 of the bull)o-spiral band within the heart divides into two distinct 

 bands, one of whicli unites with the front side of the aorta and 

 the other encircles the heart as in man and ends in the posterior 

 ligament of the aorta. The external spiral bundles have been 

 removed. In the dilated heart, fig. 19, the inner bundles are 

 unwrapped and the outer ones, which have been cut off, were 

 lengthened. In fig. 20 the opposite is the case, the inner bundles 

 including the papillary muscles are wrapped upon themselves 

 and fill the lumen of the ventricle. Specimens like the one from 

 which figs. 19 and 20 are made are not so difii(;ult to prepare and 

 they show the mechanism of contraction nnich better than the 

 illustrations do. 



What has been said about the pig's heart can easily be read 

 into the human, from the descrijition I have given of it. Fig. 7 

 shows that contraction of the bulbo-spiral band will rotate the 

 apex and wind up, or put under great stress, the chief deeper 

 bundles of the left ventricle, as shown in fig. 8. Contraction of 

 the deep bulbo-spiral band, the Triebwerk of Krehl, will then 

 complete the contraction of the ventricle. 



To obtain a proper understanding of the architecture of tlu; 

 heart the organ must be considered as a whole with a conception 

 of the function it has to perform kept uppermost, as was done 

 \)y Borelli and was emphasized by Weber and by Ludwig. Only 

 from this standpoint is it possible to get a clear understanding 

 of (his hitricate network of nuiscle bundles. Not only is this 

 the case for tin; adult heart, l)ut without it we cannot hope to 

 unravel its development, for the arrangement of the fibers nuist 

 be due to functional adaptation from the time the heart begins 

 to beat. 



