436 



until the fifth or central one, which is transverse, is reached, they 

 cross at successively wider vertical angles, as may be represented by 

 an x placed horizontally. 



Holding the cone, prepared as described, against the light, the 

 Lecturer then showed how, by the rolling process, a double system 

 of conical spirals, similar to those found in the left ventricle, had 

 been produced the one an external left-handed down system, 

 running from base to apex, and corresponding with the external 

 layers ; the other an internal right-handed up system, running from 

 apex to base, and corresponding with the internal fibres ; and how, 

 seeing the opposite systems are the result of different portions of the 

 same threads being rolled in different directions (the one within the 

 other), the spirals are consequently continuous at the apex. 



He in this manner explained the continuity of the external and 

 internal fibres at the apex. By simply producing the threads form- 

 ing the internal spirals, and turning them out at the base until they 

 met corresponding external spirals, he next showed how the con- 

 tinuity of the fibres at the base might be accounted for. The con- 

 nexion of the fibres at the base, he remarked, is effected for the most 

 part as at the apex, by continuity of their proper muscular substance ; 

 but those of the papillary muscles are continued by the tendinous 

 cords. This continuity observes a certain order, so that certain ex- 

 ternal layers are continued at the apex into certain internal layers, 

 and turn outwards at the base into their original external position. 

 Thus the first layer is continuous with the ninth, the second with 

 the eighth, the third with the seventh, and the fourth with the 

 sixth, while the fifth occupies, as already said, the middle place be- 

 tween the four external and four internal. He thus endeavoured to 

 prove that a strong analogy exists between the arrangement of the 

 fibres at the apex and the base, and that the same principle which 

 turns in the external fibres at the apex also turns out the internal 

 at the base, a view which, while it extends rather than militates 

 against that of older writers, was strongly supported by the arguments 

 he adduced. It would therefore seem that the fibres do not form 

 simple loops pointing towards the apex, as generally supposed, but 

 twisted continuous loops pointing alike to apex and base. From 

 this arrangement, it follows that the first and ninth layers embrace 

 in their convolutions those immediately beneath them, while these in 



