1870.] four Orifices of the Heart. 271 



Pig. 



Circumference. Area. 



Tricuspid 3' 6 in. 1*03 sq. in. 



Pulmonic 2*5 '49 



Mitral 3'2 -81 



Aortic 2-1 -38 



Tricuspid __1 -Q3 _ 1 .q~ 



Mitral ~ T 8l~ ' / 

 Pulmonic_ '49 



x\ortic ; 38 _ 



Difference of the ratios = '02 



Bog. 



Tricuspid 3*65 in. TO/ sq. in. 



Pulmonic 1*9 '287 



Mitral t 315 '79 



Aortic 1-6 -204 



Tricuspid_r07 _j.3g 

 Mitral "79 ~~ 



Pulmonic_ '287 

 Aortic *204 

 Difference of the ratios = '04 



Dog. 



Tricuspid 2*9 in. *69 sq. in. 



Pulmonic 1-6 '204 



Mitral 2*5 -49 



Aortic 1-4 -156 



Tricuspid _ *69 1-49 



Mitral 7 49~ 

 Pulmonic 204 j 

 Aortic -lob' _ 

 Difference of the ratios = '09 



From these facts we may fairly conclude that in the healthy human heart, 

 and most probably in the hearts of most animals, the areas of the four 

 apertures bear an exact mathematical relationship to each other, and con- 

 sequently that if the areas of any three of the openings be known, the area 

 of the fourth orifice can be correctly calculated. 



I need scarcely dwell upon the importance of a knowledge of this law in 

 estimating the amount of contraction or dilatation of orifice which a morbid 

 specimen may present. I will, however, now show from my own measure- 



