268 



Dr. Herbert Davies on the Areas of the 



[Mar. 17, 



from which data we find the areas to be : — 



Tricuspid 2*24 sq. in. 1*9 sq. in. 



Pulmonic 1*01 1 



Mitral 1'7 1*4 



Aortic *8 '71 



And if we make the same comparison of areas as we did in Dr. Peacock's 

 measurements, we find : — 



Males. 



Area of tricuspid 2*24 i .31 i 



Area of mitral 1*7 

 Area of pulmonic _ 1*01 _ 

 Area of aortic '8 



Difference of the ratios = *05 



Females. 



Area of tricuspid __ 1*9 _ j.^q 

 Area of mitral 1*4 



Area of pulmonic 1 —1-40 



Area of aortic '71 

 Difference of the ratios = '04 



It is well known that no measurements can be taken of such orifices as 

 those of the heart without liability to error ; but no one can observe 

 the close identity of the respective ratios without concluding that the 

 ratios are really identical, and that the small differences in the calculated 

 results depend entirely upon the impossibility of obtaining absolutely correct 

 measurements of the boundaries of such openings. It is clear, therefore, that 

 in whatever proportion the tricuspid is larger than the mitral, in exactly 

 the same proportion is the pulmonic larger in area than the aortic orifice. 

 This rule applies, of course, to the human heart only in its healthy state ; 

 but I shall show that its application is of practical value when we consider 

 the organ in its diseased state. 



I shall now proceed to prove that the law which I have deduced from 

 independent observations made in the healthy human heart is of far wider 

 application, for I have found by my own measurements that a comparison 

 of the areas of the same orifices in animals reveals the same result. 



The following are the facts at which I have arrived by careful and re- 

 peated measurements of the cardiac apertures in different animals. 



The measurements are individual, and not mean, and therefore less 

 liable to error. 



