IO2 Motion of the 



some animals have an auricle without any ventricle ; or 

 at all events they have a sac analogous to an auricle ; 

 or the vein itself, dilated at a particular part, performs 

 pulsations, as is seen in hornets, bees, and other insects, 

 which certain experiments of my own enable me to 

 demonstrate have not only a pulse, but a respiration in 

 that part which is called the tail, whence it is that this 

 part is elongated and contracted now more rarely, now 

 more frequently, as the creature appears to be blown 

 and to require a larger quantity of air. But of these 

 things, more in our Treatise on Respiration. 



It is in like manner evident that the auricles pulsate, 

 contract, as I have said before, and throw the blood 

 into the ventricles ; so that wherever there is a ventricle 

 an auricle is necessary, not merely that it may serve, 

 according to the general belief, as a source and maga- 

 zine for the blood : for what were the use of its 

 pulsations had it nothing to do save to contain ? No ; 

 the auricles are prime movers of the blood, especially 

 the right auricle, which is " the first to live, the last to 

 die," as already said ; whence they are subservient to 

 sending the blood into the ventricle, which, contracting 

 incontinently, more readily and forcibly expels the 

 blood already in motion; just as the ball-player can 

 strike the ball more forcibly and further if he takes it 

 on the rebound than if he simply threw it. Moreover, 

 and contrary to the general opinion, since neither the 

 heart nor anything else can dilate or distend itself so as 

 to draw aught into its cavity during the diastole, unless 

 like a sponge, it has been first compressed, and as it is 

 returning to its primary condition ; but in animals all 

 local motion proceeds from, and has its original in the 

 contraction of some part : it is consequently by the 

 contraction of the auricles that the blood is thrown 

 into the ventricles, as I have already shown, and from 

 thence, by the contraction of the ventricles, it is pro- 

 pelled and distributed. Which truth concerning local 

 motions, and how the immediate moving organ in 



