66 iii. 3 — iii. 4. 



the heart Is situated, in which we say is the principle of life and 

 the source of all motion and sensation. (For sensation and motion- 

 are exercised in the direction which we term forwards, and it is on 

 this very relation that the distinction of before and behind is 

 founded.) But where the heart is, there and surrounding it is the 

 lung. Now inspiration, which occurs for the sake of the lung and 

 for the sake of the principle which has its seat in the heart, is 

 effected through the windpipe. Since then the heart must of 

 necessity lie in the very front place of all, it follows that the 

 larynx also and the windpipe must of necessity lie in front of the 

 oesophagus. For they lead to the lung and heart,^ whereas the 

 oesophagus leads to the stomach. And it is an universal law 

 that, as regards above and below, front and back, right and left, 

 the nobler and more honourable part invariably is placed upper- 

 most, in front, and on the right, rather than in the opposite 

 positions, unless some more important object stands in the way.^'' 

 (CA. 4.) We have now dealt with the neck, the oesophagus, and 

 the windpipe, and have next to treat of the viscera. These are 

 peculiar to sanguineous animals, some of which have all of them, 

 others only a part, while no bloodless animals have any at all.^ 

 Democritus then seems to have been mistaken in the notion he 

 formed of the viscera, if he fancied that the reason why none 

 were discoverable in bloodless animals was that these animals were 

 too small to allow them to be seen. For, in sanguineous animals, 

 the heart and liver are visible enough when the body is only just 

 formed, and while it is still extremely small. For these parts are 

 to be seen in the egg sometimes as early as the third day, being 

 then no bigger than a point ; ^ and are visible also in aborted * 

 embryos, while still excessively minute. Moreover, as the external 

 organs are not precisely alike in all animals, but each creature is 

 provided with such as are suited to its special mode of life and 

 motion, so is it with the internal parts, these also differing in 

 different animals. Viscera, then, are peculiar to sanguineous 

 animals ; and this accords with the fact that the viscera are each 

 and all formed from sanguineous material, as is plainly to be seen 

 in the new-born young of these animals. For in such the viscera 

 are more sanguineous, and of greater bulk in proportion to the 

 body, than at any later period of life, because the nature of the 

 material and its abundance are most distinctly marked in objects 

 at the period of their first formation.* There is a heart, then, in 

 665 b. 



