744 THE HARVEIAN ORATIOIf. 



mammalian auricle had counted for as much in the action of the 

 heart as the bird's, its force would have been economised by the 

 placing of a large and functionally useful valve in the site of the 

 rudimentary Eustachian — a structure altogether absent in many 

 mammals, and variable, as rudimentary structures very often are, in 

 ourselves. The a priori argument of Comparative Anatomy is 

 abundantly borne out by the appeal to experiment. Marey, in his 

 'Physiologic Medicale de la Circulation du Sang,' 1863, whilst 

 referring (p. 36) to other evidence from Comparative Anatomy than 

 that which I have adduced, cites, in support of the view that the 

 auricle has but an accessory and subordinate role in the functions 

 of the heart, an experiment of Chauveau's, in which the auricle of a 

 horse, being exposed and irritated, lost its contractile power for a 

 time, during which, nevertheless, the ventricles continued to con- 

 tract and the circulation to be maintained. Colin, again (' Traite de 

 la Physiologic Comparee,' vol. ii. p. 257, 1856), found that the left 

 ventricle continued to be filled with blood even when the cor- 

 responding auricle was prevented from contracting by the insertion 

 into it of a finger. And further, Magendie had long ago noted, in 

 experimentation, what many here present may have noted in patho- 

 logical or clinical observation — viz. that the auricles may remain 

 extremely distended for hours, and, like other muscular sacs 

 similarly conditioned, unable to contract and empty themselves, 

 without the circulation for all that being brought to a standstill. 

 It was Dr. Pavy's paper, treating (in the ' Medical Times and 

 Gazette' of November 21, 1857) of the case of a man (E. Groux) 

 with a congenital fissure of the sternum, which first drew my atten- 

 tion to these points ; and his summary of what takes place in the 

 dog is so clear that I herewith reproduce it : — - 



^ In the dog, the contraction of the ventricles is sharp and rapid, 

 instead of prolonged, as in the reptile, and does not appear to occupy 

 nearly so much time as half the period of the heart's action. The 

 ventricular contraction communicates a sudden impulse to the 

 auricles, occasioning in them a distinct pulsation, which is instantly 

 followed by a peculiar thrill, wave, or vermicular movement, running 

 through the auricular parietes down towards the ventricle. This 

 thrill or wave is coincident with the passage of the blood from the 

 auricle into the ventricle, and takes place so instantaneously after the 

 ventricular contraction, that the one movement appears to run on, 



