ANIMAL MECHANICS. 



441 



equal in a healthy heart ; and that the slight preponderance 

 in favour of the right ventricle found by anatomists depends 

 on the lesser thickness of its walls, which causes it to distend 

 more than the left ventricle, under the hydrostatical pressure 

 to which it is subjected by the anatomical observer. If this 

 be so, then the principle of least action applied to the heart 

 leads to the remarkable prediction, that the lengths of the 

 common fibres ought to bear to the lengths of the proper 

 fibres the ratio of the cube rOot of 2 to unity, 



J-V5. («'4> 



Assuming this Law to be correct, we can calculate from 

 the observed lengths of the common fibres, measured in our 

 two hearts, what the length of the proper fibres ought to be, 

 and so compare our observations with theory. I find the 

 following results : — 



Comparison of Observed and Calculated lengths of Muscular 

 Fibres in the Heart of the Ox. 





Common 

 Fibre. 



Proper 

 Fibre 

 (observed). 



Proper 

 Fibre 

 (calculated). 



Difference. 



No. 1, 

 No. 2, 



13.25 in. 

 8.50 „ 



10.75 m. 

 6. 50 » 



10. 52 in. 

 6-74 „ 



+ 0. 23 in. 

 — 0. 24 „ 



These differences are less than a quarter of an inch, and 

 will be readily admitted by practical anatomists to be well 

 inside the unavoidable errors of observation. 



If there be any Naturalist who thinks it possible that a 

 mechanism such as I have here described could grow up of 

 itself, from chance combinations of fibres developed in a 



