280 



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



1. Aortic Orifice. 



volume expelled in -^W 

 Velocity through aortic or.fiee = area of aortic orifice 



_o cub. inches . ] , 

 -75 sq. in." m *** 

 = 23*1 inches in one second 

 = 2310 yards per hour. 



2. Pulmonic Orifice. 



Velocity through pulmonic orifice = f velocity through aortic opening 



= 1 7*3 inches in one second 

 = 1725 yards per hour. 



3. Tricuspid Orifice. 



... . . , 5 cub. inches 



Velocity through tricuspid = 1-75 gq. "]^ 



— 1^ inch in t4-e 1' 

 = 5 inches in one second 

 = 500 yards per hour. 



4. Mi*™* 0*-//fc*. 



Velocity through mitral =i velocity through tricuspid 

 = 7 inches in one second 

 = 700 yards per hour. 



The mean velocities of the currents of blood traversing a healthy heart, 

 with the dimensions of the areas as given above, are as follows : — 



yards. mile. 

 Aortic = 2310 = 1*3 per hour 

 Pulmonic = 1725 = 1 nearly 

 Mitral = 700 = '4 

 Tricuspid = 500 = -28 



In such a heart we see, therefore, that the blood enters the tricuspid 

 orifice at the rate of nearly J mile per hour, and leaves it through the 

 aortic orifice at the rate of nearly 1| mile per hour; and that the ve- 

 locity, therefore, of the tricuspid incoming current is only one-fifth of 

 the velocity of the stream which passes through the aortic orifice. 



Without entering into arithmetical details, such a result as the above 

 is easily arrived at when we bear in mind the facts that the same quan- 

 tity of blood passes through the two openings, but that while the tri- 

 cuspid is, according to Dr. Peacock, 2|, and according to Dr. Reid 

 nearly three times larger than the aortic orifice, the flow of the three 

 ounces through the former occupies nearly twice the time required by 



