462 MODERN DEVELOPMENTS OF HARVEY's WORK. 



wrongly glorified at the exx)eiise of the past, and past Avork or past 

 benefits are forgotten. 



Clood exaiiii)les of tliis are atforded by physiological views regarding 

 the action of the vena cava and i)nlmonary veins and the causation of 

 the cardiac sounds. Harvey appears to have thought that the vena 

 cava and pulmonary veins were simply dilated i)assively by the pas- 

 sage of blood into them; but the fact that they possess a power of inde- 

 ])endent pulsation was known to Haller/and was brought prominently 

 forward by Senac,'^ who regards the vena cava as the starting point of 

 the whole circidation. He says: "The vena cava is therefore the first 

 motor cause which dilates. the cavities of the heart; it tills the auricles, 

 and extends their walls in every direction." 



These observations appear to have been almost forgotten uutil they 

 Avere again made independently a few years ago,^ and in one of the 

 latest and most accurate physiological treatises which now exist the , 

 description of the cardiac cycle is nearly the same as that given by 

 Senac. "A complete beat of the whole heart, or cardiac cycle, may be 

 observed to take place as follows: 



" The great veins, inferior and superior vente caviX", and pulmonary 

 veins are seen, while full of blood, to contract in the neighborliood of 

 the heart; the contraction runs in a ])eristaltic wave toward the auri- 

 cles, increasing m intensity as it goes."^ 



The pulsation of these veins, however, can not be a constant phe- 

 nomenon, or it would have been noticed by such a keen observer as 

 Harvey. 



The sounds of the heart were discovered by Harvey, or at least Avere 

 known to hiin, for he speaks of the sound caused in the esophagus of 

 the horse by drinking, and says: "In the same way it is with each 

 motion of the heart, when there is a delivery of blood from the veins 

 to the arteries, that a i)ulse takes place and can be heard within the 

 chest." This observation remained, as far as we know, without any 

 farther development until the time of Laeunec, who introduced the 

 practice of auscultation; but it was a fellow of this college. Dr. Wol- 

 lastoii,'' who first discovered that the muscles daring contraction giv^e 

 out a sound; and although many observations were made regarding 

 cardiac murmars by Corrigan, Bouillaud, and Piorry, it was chielly by 

 fellows of this college, Dr. Clendinning, Dr. C. J. !>. Williams, and Dr. 

 Todd, that the cjuestion was finally settled, and the conclusions at which 

 they arrived are those now accepted as correct, viz, that "the first or 

 systolic sound is essentially caused by the sudden and forcible tight- 

 ening of the muscular fibers of the ventricle when they contract; and 

 that the second sound Avhich accompanies the diastole of the ventricle 



' Haller. Elementa Pbysiologiiv, 1757, Toiue I, pages 410 and 399. 



-Senac. De la Structure du Cwur, Livre IV, Chapter III, page 24. 



sProc. Roy. Soc, 1876, No. 172. 



■*M. Foster. Text-boolc of Physiology, Gth ed., Part I, Chapter IV, page 231. 



6 Wollaston. Phil. Trans., 1810, page 2. 



