272 



Dr. Herbert Davies on the Areas of the [Mar. 17, 



ments how this law was applied, and how closely the observed and calcu- 

 lated results agreed in the case of a strong healthy man who died in the 

 London Hospital from the effects of a fractured spine. The heart was 

 perfectly healthy. I carefully measured the pulmonic, mitral, anfl aortic 

 orifices, calculated the area of the tricuspid, and then measured its circum- 

 ference. Having worked out its area, I was able to observe what difference 

 existed between the result of actual measurement and the result derived 

 from " the law of the orifices " which I had discovered. 



Human Heart. 



Circumference 



Pulmonic 3*55 in. 



Mitral 4-20 



Aortic 3*10 



Now, by the law of the orifices, 



Area of tricuspid Area of pulmonic 



Area of mitral Area of aortic ' 



.\ area of tricuspid= 1*405 X-!-^^ 



'/i)D 



= 1-972. 



By measurement, — 



Circumference. Area. 

 Tricuspid=5 , l in. 2'070 sq. in. 



Area of tricuspid by measurement^ 2*0/0 sq. in. 

 Area of tricuspid by calculation = l'9/2 



Difference between calculated and 



observed results = '098 



The calculated and observed results differ so little from each other, that 

 this case evidently strongly corroborates the correctness of the law which I 

 believe regulates the relative magnitude of the areas of the four cardiac 

 openings. 



If, moreover, we scrutinize the measurements, we shall observe an 

 equally important fact, that the ratio of the areas of any two corresponding 

 orifices is almost constant in the same, and, I may almost add, in all 

 animals, man included. 



Thus the area of the tricuspid is nearly 1*3 times the area of the mitral 

 orifice, and the area of the pulmonic of course bears the same proportion 

 to that of the aortic opening. By measuring, therefore, the two orifices of 

 the right (supposed healthy), we are enabled by this law to deduce ap- 

 proximately the magnitude of the areas of those of the left heart, and 

 vice versa. One healthy orifice being known, the area of the corresponding 

 opening in the other side of the heart can be approximately calculated ; 

 and should the latter be diseased, its deviation from the normal area can be 



Area. 

 1-003 sq.in. 

 1-405 

 •765 



