Caption in article:

'Sketch of the section of heart of adult Rat, showing junction of right auricle and ventricle. In the upper part of the figure is the outer wall of the right auricle, below and to the right is the wall of the right ventricle, and below and more to the left is the mass of tissue from which springs the auriculo-ventricular valve. The cavity of the heart is to the left. It is seen that a band of muscle runs almost completely round from auricle to ventricle, bordering closely upon the cavity of the heart. At the lower part this band becomes continuous with a network of branched muscle cells lying in the interval between auricle and ventricle. These branched fibres become continuous on the right with the muscular tissue of the ventricle.' (244)