. Carnegie Institution of Washington publication. 182. .183 FIGS. 179, 180. Sciurut vulgarit a-Oxy hemoglobin. Fias. 181, 182,183. Sciurua vulgaris J3-Oxyhemoglobin. Habit tabular, in thin hexagonal plates consisting of the short prism and the base, with a ratio of breadth of plate to its thickness of about 10 : 1 (text figure 179). The plates are variable in size and are not all equally developed on all faces of the prism, but the majority are strictly hexagonal in development, as they all are in angles. Many, however, show a distinctly orthorhombic development, two opposite faces being much
. Carnegie Institution of Washington publication. 182. .183 FIGS. 179, 180. Sciurut vulgarit a-Oxy hemoglobin. Fias. 181, 182,183. Sciurua vulgaris J3-Oxyhemoglobin. Habit tabular, in thin hexagonal plates consisting of the short prism and the base, with a ratio of breadth of plate to its thickness of about 10 : 1 (text figure 179). The plates are variable in size and are not all equally developed on all faces of the prism, but the majority are strictly hexagonal in development, as they all are in angles. Many, however, show a distinctly orthorhombic development, two opposite faces being much larger than the other four. No distinctly rhombic plates were seen, as in the crystals from the putrid blood. Many irregular crystals can be seen in the photographs, they are broken parts of twins. The plates occurred singly or piled on the basal surfaces into irregular parallel growths. Twins occurred, interpenetrant and contact; sometimes the crystals on edge showed a rough six-pointed star from three interpenetrant crystals (text figure 180). These are evidently due to twinning on a second-order pyramid, and the angle of two of the plates with one is about 54° for each. Apparently there are two second-order pyramids that become twin planes, and they would be (12T2) and (12T1). These are not always interpenetrant; some are simply juxtaposed. A twin on the first-order pyramid was also observed. The color is rather pale oxyhemoglobin red, but this is due to the thin crystals, and it was of course quite strong on edge views. Pleochroism is scarcely noticeable, but the absorption seemed to be slightly stronger for w. Double refraction is very weak; on the flat the crystals are singly refracting, but on edge the weak double refraction may be observed, with difficulty, by means of the quartz wedge. They are then seen to extinguish parallel to the base. The symmetry axis is the axis of less elasticity, or w > s and the optical character is slightly positive. On the basal aspect
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