1870.] 



four Orifices of the Heart, 



273 



determined, and the amount of abnormal contraction or dilatation fairly 

 estimated. 



To illustrate the value of this approximative law, I will exemplify, in a 

 case of mitral constriction detailed by Dr. Walshe (Diseases of the Heart 

 p. 3/3), the mode in which the amount of constriction may be calculated. 



Mitral Constriction. 



Circumference. Area. 



Tricuspid 4^ = 4*875 in. l*9sq. in. 



Pulmonic .31=3-125 '77 



Mitral l£=l'8/5 -28 



Aortic 2f=2-375. -45 



Tricuspid 1*9 „ i 

 v r . , - = — T^s = / i nearly. 

 Mitral -28 J 



Pulmonic '77 , _ 7 



— i — = —. = 1*7, nearly. 



Aortic *45 



Hence the tricuspid (by reason of the extreme narrowing of the mitral 

 opening) is seven times larger in area than the latter orifice, in place of 

 being only 1*3 to 1*4 times larger in area. If we suppose the tricuspid to 

 be nearly normal, then as 



Area of tricuspid = nearl 

 Area of mitral 



.-. area of mitral (healthy) = area °[ ' ricus P iJ 



= — ? = 1*45 sq. in. 

 1-3 4 



Hence the amount of the contraction of 



the mitral orifice = 1*45, the normal size 

 — *28, its actual size. 



== 1-17 sq. in. 



" The diseased aperture just admitted the end of the index figure ; its 

 edge was rugose, and the valve w r as funnel-shaped towards the ventricle. 

 The left auricle was much hypertrophied, its walls in some parts being J 

 inch in thickness, and its endocardium creaked on being touched." The 

 pulmonic is evidently large in proportion to the aortic opening (the ratio 

 being 1*7 instead of 1*3 to 1*4) ; and there was no doubt considerable hy- 

 pertrophy and dilatation of the right ventricle. The increase in the area 

 of the pulmonic aperture was the direct result of this condition of the right 

 side of the heart. The tricuspid was also probably somewhat dilated, as 

 the "valves looked insufficient to fill the widened orifice," and the jugular 

 veins appeared during life to be swollen and pulsatory ; but the absolute 

 size of the tricuspid shows that the dilatation was not excessive. The 

 area of the aortic opening appears to be below the mean amount. Was 



VOL. XVIII. Y 



