Rabbits are, as is well known, extremely timid animals, and it is remarkable that no other blushes and grows pale so easily as the rabbit. The changes in circulation produced by psychical impressions and by the emotions are more observable in the ears than in the face, as is indeed the case with many men. In Northern Italy, after someone has received a vigorous scolding, I have heard the popular expression used: 'He caught it hot enough to make his ears turn red.’ In the middle of the auricle of the rabbit’s ear there is an artery, running from the base to the summit, which ramifies and winds in such a manner as to form two veins on the edge of the auricle. In 1854, Moritz Schiff observed that this artery showed alternate movements of contraction and expansion, not corresponding to the systole and diastole of the heart. If one looks at the rabbit’s ear against the light, from time to time one sees the artery decrease in diameter, until at last it quite disappears, then it increases again, and, as it swells, it expands all its branches, so that the whole ear becomes of a vivid red and also warmer. This fulness of blood in the ear lasts a few seconds, then artery and branches contract and the redness gradually dies away. Schiff called this artery an accessory heart, because he imagined that the contractions and expansions observed by him in the vessels of the ear were to promote a better circulation of blood in the ear of the rabbit, just as the heart does for the rest of the body.