HEART. 



591 



the muscular fibres of the ventricles may be 

 stated to be as follows. 1st, Most of these 

 fibres are connected by both extremities to the 

 tendinous structure of the heart, a tact well 

 known to Lower,* though overlooked by many 

 subsequent anatomists. 2d, The direction of 

 these fibres is more or less oblique, a com- 

 paratively small part of them only being 

 vertical, and that too for a limited' part of 

 their course. The degree of obliquity of 

 these spiral turns is different in different por- 

 tions of the heart : they are more ob- 

 lique on the surface and less oblique 

 as we proceed to the deeper fibres, 

 more particularly at the base. The 

 deeper fibres approach more to the cir- 

 cular form. 3d, As has been already 

 stated, part of these fibres are common 

 to both ventricles; while part only 

 belong exclusively to a single ventricle, 

 and that principally at the base. 4th, 

 The external fibres are longer than the 

 next in order, and after turning round 

 the apex pass upwards into the interior, 

 below the lower margin of the shorter 

 fibres, and form the inner surface of 

 the ventricles, while the deeper again 

 turn up below the lower margin of the 

 fibres next in succession, so that the 

 longer enclose by their two extremities 

 all the shorter fibres. By this arrange- 

 ment we can explain how the base and 

 middle part of the ventricles should 

 be much thicker than the apex. This 

 arrangement has been particularly in- 

 sisted upon by Dr. Duncan and Gerdy, 

 and to illustrate it Gerdy has given an 

 ideal illustration, of which fig. 271 is a 

 copy. 



Fig. 271. 



run in a spiral manner from above downwards 

 and from right to left, while those on the pos- 

 terior surface, which are in general more ver- 

 tical, run from left to right. Most of these 

 bands are thin and broad at the upper part, 

 and become narrower and thicker as they ap- 

 proach the apex, where they form a remarkable 

 twisting, which has been termed the vortex, 

 (of which jig. 272, taken from the human heart 

 after boiling, is an accurate representation,) and 

 then pass in to assist in forming the inner surface 



Fig. 272. 



of the left ventricle and the columnae carnece. 

 The manner in which the external fibres turn 

 in at the apex to form the inner surface of the 

 ventricles and enclose the deeper fibres was 

 well known to Lower, and he has illustrated 

 it by an engraving, of which Jig. 273 is a copy. 



Fig. 273. 



In examining the course of the fibres of the 

 ventricles we shall not attempt to describe each 

 particular band of fibres, but confine ourselves 

 to their general arrangement.f In examining 

 the surface of the ventricles the superficial 

 fibres of the anterior surface are observed to 



* Tractatus de Corde. p. 34 to 37. Lugd. Batav. 

 1669. 



t Wolff has named and minutely described eight 

 distinct bands of muscular fibres on the surface of 

 the right ventricle : Acta Petropolit. pro anno 1781, 

 torn. viii. p. 251, 1785. 



