36 Eustachian — a structure altogether absent in many mammals, and variable, as rudi- mentary structures very often are, in our- selves. The d priori argument of Com- parative Anatomy is abundantly borne out by the appeal to experiment. Marey, in his ' Physiologie Medicale de la Circulation du Sang,' 1863, whilst referring (p. 36) to other evidence from Comparative Anatomy than that which I have adduced, cites, in support of the view that the auricle has but an accessory and subordinate role in the func- tions of the heart, an experiment of Chau- veau's, in which the auricle of a horse, being exposed and irritated, lost its contractile power for a time, during which, neverthe- less, the ventricles continued to contract and the circulation to be maintained. Colin, again (Traits de la Physiologie Comparee, vol. ii. p. 257, 1856), found that the left ventricle continued to be filled with blood even when the corresponding auricle was prevented from contracting by the insertion into it of a finger. And further, Magendie had long ago noted, in experimentation, what many here present may have noted
