MUSCULAR ARCHITECTURE OF THE HUMAN HEART 265 



It is apparent that the aiTangement of the superficial fibers of 

 the heart is such that their contraction will cause the heart to 

 rotate, as is well known to physiologists. In so doing the trans- 

 verse diameter of the heart must diminish but it is not necessary 

 that the long diameter should change as was pointed out by 

 Hesse. ''^ Since the rotation of the apex in contraction is accom- 

 panied by a straightening of the superficial spiral fibers, it must 

 cause the inner spiral fibers to curve upon themselves for they 

 run at right angles to the outer fibers. This is well illustrated 

 in a diagram by Nicolai,^* which shows that in contraction the 

 outer fibers of the ventricle become straighter, while the inner 

 ones become more spiral. According to my description of the 

 heart muscle fasciculi such a contraction need not change the 

 length of the heart, but it exaggerates to the utmost the folds 

 which are formed within the heart during systole; in fact the 

 lumen of the left ventricle is nearly obliterated. In fig. 19 the 

 heart, which is held in both hands, is represented as it is in dias- 

 tole. In order to imitate contraction of the heart as it takes 

 place in systole it is necessary to rotate the apex as shown in 

 fig. 20. In this change of position the inner bundles are twisted 

 as one wrings out a wet rag. This was Borelli's^*^ conception of 

 the heart contraction which I do not believe can be improved on 

 very much. Borelli gives an account of the arrangement of the 

 muscle bundles of the heart in which it is pointed out that there 

 is a general downward course of the fibers from the base to the 

 apex where they form the vortex. He also gives a figure of two 

 hands twisting a rope to illustrate the way the rotation of the 

 contracting heart presses the blood out during systole. My dis- 



^^ The statement to this effect by Hesse, His and Braunc's Archiv, 1880, reUxtes 

 to the dog's heart. Krehl, I.e., p. 349, thinks that it is equally applicable to the 

 human heart, although evidence is wanting. 



^^ Nicolai, Nagel's Handbuch der Physiologic, Braunenschweig, 1909, Bd. 1, 

 fig. 74. Nicolai's description is entirely theoretical for he states that the architec- 

 ture of the heart is l>y no means clear, and that the longer this subject is worked 

 upon the more confused it becomes. Evidently Nicolai has neither studied suit- 

 able specimens, nor the literature upon the subject. It is becaue of the importance 

 of NageFs Handbuch that I call attention to Nicolai's dilemma. 



■'o Borelli. De motu animalium, Romae, 1681. 



