 For this reason we should not be childishly disgusted at the examination of the less valuable animals. For in all natural things there is something marvelous. Even as Heraclitus is said to have spoken to those strangers who wished to meet him but stopped as they were approaching when they saw him warming himself at the oven—he bade them to enter without fear, ‘For there are gods here too’—so too one should approach research about each of the animals without disgust, since in every one there is something natural and good. For what is not haphazard but rather for the sake of something is in fact present most of all in the works of nature; the end for the sake of which takes the place of the good. If someone considered the study of the other animals to lack value, he ought to think the same thing about himself as well; for it is impossible to look at that from which mankind has been constituted—blood, flesh, bones, blood vessels, and other such parts—without considerable disgust. Just as one who discusses the parts or equipment of anything should not be thought of as doing so in order to draw attention to the matter, nor for the sake of the matter, but rather in order to draw attention to the overall shape (e.g. to a house rather than bricks, mortar, and timbers); likewise one should consider the discussion of nature to be referring to the composite and the overall substantial being rather than to those things which do not exist when separated from their substantial being. (PA I 5, 645a4–36)