VOL. XXIV.] PHILOSOPHICAL TRANSACTIONS. 217 



from its natural size, but was not, by two parts in three, so large as the left 

 ventricle of the heart of a subject I have dissected. The symptoms, some 

 years before the (jeath of this person, who was about 40 years of age, were ex- 

 traordinary shortness of breath, especially on any fatigue, with an intermission 

 of one stroke in three of the pulse; the posture of sitting up was more eligible 

 than any other; he complained of great faintness, and now and then pain about 

 the heart, the extreme parts often cold, which towards his death increased 

 more and more on him ; his legs and arms being mortified some hours before. 

 On opening the chest, the heart, particularly its left ventricle, was found larger 

 than that of an ordinary ox, and filled with coagulated blood ; the valves of 

 the great artery aa, fig. 1 1 , were petrified, insomuch that they could not ap- 

 proach each other, as expressed fig. \2 and 14 ; but an orifice, represented at 

 fig. 15, remained always open by the petrifactions bb, fig. 13, and aa, fig. 15, 

 which had clogged these valves, and hindered their application to each other, 

 as in a natural state is represented in fig. 12 and 14, aaa. 



The explication of the symptoms in both these cases is obvious enough : for 

 though the person in the first instance did not die of the same disease as the 

 other, yet the symptoms in his illness plainly showed what must follow, from 

 the disorders of these valves, as they are rendered more or less useless ; for as 

 their office is to prevent the return of the blood into the heart, in its diastole, 

 by exactly shutting up the passage of the aorta, like the valves in water engines, 

 so if by any accident they are hindered from doing their duty, as they were by 

 tjie petrifactions mentioned, the consequences must be, not only a regurgita- 

 tion of blood into the heart, but they baulk its impulsive force, when the mus- 

 cular fibres in these valves cannot contract, to prepare the passage for the blood 

 of the left ventricle, when it is to be expelled into the aorta. Hence the inter- 

 missions of the pulse in the first instance may be accounted for. In the latter 

 instance, these valves were wholly useless, and the circulation became more 

 difficult, as appeared by the refrigeration of the extreme parts, the mortifica- 

 tions, &c. In both these cases, the left ventricle of the heart was dilated 

 proportionably to the bad constitution of these valves, which plainly shows these 

 valves give such assistance to the heart, as it cannot be without, and that it 

 gradually suffers according to their indisposition. 



Before these papers were sent to the press, I had an opportunity of observing 

 a like instance of that first mentioned, in an elderly gentleman, about 72, who 

 sometimes had intermissions in his pulse several years before his death, in whom 

 I found divers petrifactions in the mitral and semilunar valves of the left ven- 

 tricle of the heart. 



VOL. V. F » 



