'In order to make out the structure and relations of the disk it is necessary to have recourse to preparations made in various ways. The most instructive were obtained by embedding the organ in cacao butter, after prolonged hardening in alcohol or chromic acid, or by embedding in the usual way in paraffin and staining with logwood, or by placing fresh sections of the frozen organ into 2 per cent. solution of ammonium bichromate for some days and then staining them with picro carmine (which stains the disk) or logwood. The facts to be learned from such preparations are exhibited somewhat diagrammatically in Fig. 3. It is seen that the flat anterior surface of the disk is formed by a layer of semitransparent (cloudy) material, of even thickness (about 1/3 µ), and beset at very regular intervals with flattened nuclei, each of which measures about 0.6µ. Underneath this structure the substance of the disk is made up of parallel laminae, which in section presents the striated appearance shown in the drawing. These strive are about 0.2µ apart, and split readily into fine laminae, so that in section they present the character of wavy fibres separated from each other by vacant spaces. The thickness of this layer, which we propose to call the striated lamina, is about 3µ. On its posterior aspect we again come to material of the same cloudy appearance as that which forms the nucleated layer of the anterior surface, but here it stretches out into long projections, which, from the form presented by their longitudinal sections, might be supposed to be papillae, but are seen on transverse section to be anastomosing ridges enclosing round or oval alveoli. As there is always a marginal ridge (seen in longitudinal sections at each end), the posterior surface may be described as presenting a number of pits separated from each other by ridges and surrounded by a marginal wall. As to the physiological meaning of the disk, and the two kinds of material of which it is composed, all that can be said is that it is a supporting structure for the end organ. The alveolated arrangement of its under surface might be explained as calculated to favour blood supply by presenting the largest possible surface.' (143-144)