MUSCULAR ARCHITECTURE OF THE HUMAN HEART 261 



corresponding points marked by an X. In fact this bundle 

 arises in common with the superficial bulbo-spiral band from the 

 membranous septum and could be well considered with it (fig. 

 10, LRV and BS). If described with it it would be said to extend 

 on the outside of the heart to the apex and thence through the sep- 

 tum, and on the inside of the right ventricle over the septum, 

 finally ending in the papillary muscles of the left ventricle. It 

 also ends in the large papillary muscles of the right ventricle. 



MacCallum found that he could unroll foetal pigs' hearts which 

 had been macerated in a solution of glycerine, water and nitric 

 acid, into a single sheet or scroll of fibers. He was also able to 

 unroll a number of foetal hearts as well as the heart of a child 

 three or four years old. Subsequently Knower showed that 

 hearts from cadavers which had been embalmed with carbolic 

 acid could be unrolled by MacCallum's method with consider- 

 able ease. Since, however, my aim now is to interpret Mac- 

 Callum's scroll, I shall use the adult pig's heart in my descrip- 

 tions. I have extended his work by leaving the tendons at the 

 base of the heart intact in order to show better the attachment 

 of the fiber bundles at this point. The specimens were pre- 

 pared by distending them with a three per cent solution of 

 carbolic acid in water as already described. ^^ They were then 

 dissected, as shown in figs. 3 and 4. In doing so it is well to let 

 the split be natural and not forced either to one side or to the 

 other.^^ Soon the longitudinal muscle band from the mem- 

 branous septum to the right ventricle comes into view and after 

 it has been well isolated it is to be cut squarely. Next the aorta 

 is to be torn from its root which takes with it the muscle bundles, 

 superficial and deep bulbo-spiral, arising at this point. This 

 may be understood by a glance at figs. 10 and 11. The splitting 



'^ By this method hearts may be prepared in either the dilated or the con- 

 tracted form. In order to make specimens rapidly and also quite satisfactorily 

 hearts may be unrolled after boiling them in dilute acetic acid for half an hour. 

 The specimen can then be cleaned easily, the muscle is not shrunken and the 

 tendons at the base are still intact. 



" Searle, Todd's Cyclopaedia of Anatomy, 1836, vol. 2, evidently had this sheet 

 before him when he described the "rope" of the heart. His fig. 278 is similar to 

 my fig. 17. 



