VOL. XXIX.] PHILOSOPHICAL TRANSACTIONS. 183 



ventricle. It is not improbable but the firm adhesion of the capsula cordis 

 membranosa to the substance of the heart, occasioned that uncommon trem- 

 bling and throbbing : its free and easy motion being hindered by that thick in- 

 volucrum which surrounded it so close on each side. The learned Dr. Lower, 

 in his elaborate treatise de Corde humano, gives such an instance, and explains 

 the palpitation after this manner. 



As for the second, viz. the dilatation of the left ventricle and muscular bag 

 of the pulmonary vein ; that is altogether owing to the bad configuration of the 

 valves we have now described: for as the great artery, or aorta, arises out of this 

 ventricle, it has three valves, which separating give passage to the blood from 

 the ventricle into the vessel ; and in a natural state they shut that passage, and 

 so prevent the blood from recoiling into the same, if it should endeavour to re- 

 turn. But in this case, by reason of its contracted narrowness and thickness, 

 not being able to close or shut the passage, the blood flowed back again into 

 the cavity, which it had gradually enlarged, and dilated to the size we see. 

 Besides the muscular valves not being duly qualified for the performance of their 

 office, the blood recoiled into the auricle, which it had distended in the like 

 manner. This constant regurgitation, or reflux of the blood, is besides suffici- 

 ent of itself to produce this extraordinary trembling, or TraKuog Ka^^ta?, as the 

 Greeks call it. 



y/ ready Description and Quadrature of a Curve of the Third Order, resembling 

 that commonly called the Foliate. By Mr, Abr. de Moivre, F, E. S, 

 N° 345, p. 329. 



I have looked a little farther into that curve which fell lately under my con- 

 sideration. It is not the foliate as I first imagined, but I believe it ought not to 

 make a species distinct from it. aeb (fig. 7, ph 4) is the curve I thus describe. 

 Let AB and bk be perpendicular to each other. From the point a draw ar 

 cutting BK in r, and make re = br, the point e belongs to the curve. Draw 

 Bc making an angle of 45° with ab; this line bc touches the curve in b. From 

 the point e draw ed perpendicular to bc, and calling bd, x; de, y; ab, a; and 

 making |/8aa = n, the equation belonging to that curve is x^ -\- ocxy ■\- xyy 

 + 3/^ = nxy, or — — ^ = nxy. Taking bg = ab, and drawing gp perpendi- 

 cular to BG, PG is an asymptote. In the foliate, the equation is a^ -\- y^ =. 

 ^nxy ; in which the two terms xocy -\- xyy of the former equation are wanting ; 

 and its asymptote is distant from b by 4-ba. Again, draw ep perpendicular to 

 ab : let BF be called z, and fe, v; the equation belonging to the curve aeb is vv=: 



