188 



PHYSIOLOGY 



CHAP. 



1. That the position of elastic equilibrium of the semilunar 

 valves corresponds not with closure but with half -opening 

 (Fig. 56). 



2. That during the systolic efflux the three sinuses of Valsalva 

 and the bulbus arteriosus dilate, and the semilunars assume and 

 maintain a half-opened position, with vibration of their free 

 borders, which therefore become blurred and give rise to a muffled 

 sound. 



3. That at the cessation of systole (systolic dead point) the 



valves close rapidly and then reopen, 

 if systole is not followed by diastole. 



4. That when diastole follows 

 systole, the valves (which were 

 already closed at the systolic dead 

 point) extend towards the con us 

 arteriosus of the ventricle, forming 

 with their surfaces a tetrahedron, 

 with the point directed upwards, 

 and emit a short sound which is of 

 higher pitch than the preceding. 



From these results it is obvious 

 that the closing of the seinilunars 



the effect not of commencing 



Km. .Jli. Diagrammatic section, life s 

 across sinus of art. pnlmonaris 

 pig ; constructed by Ueradini 



of 



s 



average of five measurements. The 

 figure shows the position of equilibrium 



of the free borders of the seinilunar 

 valves. A, li, C, and n, h, r, represent 



from diastole, but of the close of systole. 



f ' V k " T 1 



It is easy to see that no reflux is 

 possible under these conditions, since 



the largest and 'the least equilateral tllCValvCS ai'6 already closed at the 

 triangle that ean be described by the ... , . 



beginning ot diastole, and when 

 thrown into elastic tension do but 

 keep up this position of closure. 



When, according to Ceradini's 



three outlines ('_'<, //;/;, l>Aa) of the 

 sinuses nf Valsalva. The circle sur- 

 rounding the smallest triangle repre- 

 sents the projection of the constric- 

 tion of the artery which divides 

 the sinoid from the bulbar portion. 



different equilibrium from that of the 

 two lateral valves, -//. 



of 



The valve r, which corresponds to the 



anterior surface of the heart, has a method, diastole IS imitated by 



ing with the half-open position 

 the valves, their closure is obtained 

 by a reflux, and the amount of fluid which under these condi- 

 tions regurgitates from artery to ventricle can be measured. 

 According to Ceradini, this would be considerable, amounting to a 

 seventh part of the flow that leaves the ventricle at systole. This 

 proves the importance of the pre-diastolic closure of the semilunar 

 valves, which normally prevents the loss of a considerable part of 

 the useful effect of the cardiac cycle. 



In repeating the experiment, with Ceradini's apparatus, we 

 found several inconveniences, which we attempted to eliminate by 

 modifications indispensable to the demonstration of the play of the 

 valves before any large audience. Fig. 57 shows this improved 

 apparatus. 



The theoretical explanation of the mechanism of the valves 



