CIRCULATION OP THE BLOOD 143 



totle has it*) is contractile; in which way the word veu/oow 

 is derived from veua>, nuto, contraho; and if I am permitted 

 to proceed in my purpose of making a particular demonstra- 

 tion of the organs of motion in animals from observations 

 in my possession, I trust I shall be able to make sufficiently 

 plain how Aristotle was acquainted with the muscles, and 

 advisedly referred all motion in animals to the nerves, or to 

 the contractile element, and, therefore, called those little 

 bands in the heart nerves. 



But that we may proceed with the subject which we have 

 in hand, viz., the use of the auricles in filling the ventricles, 

 we should expect that the more dense and compact the heart, 

 the thicker its parietes, the stronger and more muscular must 

 be the auricle to force and fill it, and vice versa. Now this t 

 is actually so: in some the auricle presents itself as a san- 

 guinolent vesicle, as a thin membrane containing blood, as in 

 fishes, in which the sac that stands in lieu of the auricles 

 is of such delicacy and ample capacity that it seems to be 

 suspended or to float above the heart. In those fishes in 

 which the sac is somewhat more fleshy, as in the carp, 

 barbel, tench, and others, it bears a wonderful and strong 

 resemblance to the lungs. 



In some men of sturdier frame and stouter make the right 

 auricle is so strong, and so curiously constructed on its inner 

 surface of bands and variously interlacing fibres, that it 

 seems to equal in strength the ventricle of the heart in other 

 subjects; and I must say that I am astonished to find such 

 diversity in this particular in different individuals. It is to 

 be observed, however, that in the foetus the auricles are out 

 of all proportion large, which is because they are present be- 

 fore the heart makes its appearance or suffices for its office even 

 when it has appeared, and they, therefore, have, as it were, 

 the duty of the whole heart committed to them, as has al- 

 ready been demonstrated. But what I have observed in the 

 formation of the foetus, as before remarked (and Aristotle 

 had already confirmed all in studying the incubated egg), 

 throws the greatest light and likelihood upon the point. 

 Whilst the foetus is yet in the form of a soft worm, or, 

 as is commonly said, in the milk, there is a mere bloody 



In the book de Splritu, and elsewhere. 



