MUSCULAR ARCHITECTURE OF THE HUMAN HEART 215 



more marked on the right side of the heart than on the left and 

 in front than behind. The most sharply defined parallel fibers 

 are found crossing the posterior longitudinal sulcus. 



I shall speak of a group of fibers as a fasciculus and a number 

 of them side by side, sufficiently collected to be pulled off together, 

 as a sheet. I wish to repeat that the fasciculi and sheets are 

 never fully separated from adjacent fasciculi or sheets, but are 

 in constant communication with them. The fasciculus marks 

 the chief direction of the fibrils which can be stripped off with 

 considerable ease, and pass in the direction in which the muscle 

 shortens in contracting. 



Schema A. The outer and inner bundles are continuous at the apex as V-shaped 

 loops with very acute angles. Somewhat deeper the angle at the point of turning 

 is a right angle and in the middle layer the bend forms an obtuse angle. 



No simple schema can be given which applies equally well 

 to all portions of the heart wall. In general the wall is composed 

 of V-shaped loops lying within one another, the outer forming 

 very acute angles at the heart apex, with one stem of the V on 

 the outside of the heart and the other on the inside (Schema A). 

 Passing towards the middle of the ventricle wall the V-shaped 

 loops do not reach to the apex, and the angle is less acute. Fin- 

 ally as they come to lie in the middle of the wall the V's form 

 quite obtuse angles. This change may be said to be due to the 

 lateral anastomoses of fasciculi becoming greater than the main 



