Heart and Blood 99 



the whole body, both ventricles have in fact the same 

 office to perform, whence their equality of constitution. 

 It is only when the lungs come to be used, and it is 

 requisite that the passages indicated should be blocked 

 up, that the differences in point of strength and other 

 things between the two ventricles begin to be apparent : 

 in the altered circumstances the right has only to 

 throw the blood through the lungs, whilst the left has 

 to impel it through the whole body. 



There are further within the heart numerous braces, 

 so to speak, fleshy columns and fibrous bands, 

 which Aristotle, in his third book on Respiration, and 

 the Parts of Animals, entitles nerves. These are 

 variously extended, and are either distinct or contained 

 in grooves in the walls and partition, where they 

 occasion numerous pits or depressions. They constitute 

 a kind of small muscles, which are superadded and 

 supplementary to the heart, assisting it to execute a 

 more powerful and perfect contraction, and so proving 

 subservient to the complete expulsion of the blood. 

 They are in some sort like the elaborate and artful 

 arrangement of ropes in a ship, bracing the heart on 

 every side as it contracts, and so enabling it more 

 effectually and forcibly to expel the charge of blood 

 from its ventricles. This much is plain, at all events, 

 that some animals have them strongly marked, others 

 have them less so ; and, in all that have them, they 

 are more numerous and stronger in the left than in 

 the right ventricle ; and whilst some have them in the 

 left, there are yet none present in the right ventricle. 

 In the human subject, again, these fleshy columns and 

 braces are more numerous in the left than in the right 

 ventricle, and they are more abundant in the ventricles 

 than in the auricles ; occasionally, indeed, in the 

 auricles there appear to be none present whatsoever. 

 In large, more muscular and hardier bodies, as of 

 countrymen, they are numerous ; in more slender 

 frames and in females they are fewer. 



