CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



219 



the putrid blood were of a different type from those of the fresh blood, and 

 they will be described separately. They are, nevertheless, probably both 

 the same substance, but the crystals from the putrid blood probably throw 

 light on the actual structure of the crystals in all species of Sciurus. The 

 two types of crystal will be distinguished as a-oxyhemoglobin (from the 

 fresh blood) and /3-oxyhemoglobin (from the putrid blood). 



a-Oxy hemoglobin of Sciurus vulgaris, from the Fresh Blood. 



Hexagonal (or pseudohexagonal) : No axial ratio determinable. 

 Forms: Unit prism (10TO), base (0001). 

 Angles: Prism angle 60; prism to base 90. 



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 a very faint dusky 

 cross in convergent light shows the uniaxial character of the crystals. 



^-Oxyhemoglobin of Sciurus vulgaris, from the Putrid Blood. 



Orthorhombic: Axial ratio a : b : c =0.577 : 1 : c. 



Forms observed: Unit prism (110), base (001). 



Angles: Prism angle 110 A 110=60; prism to base 110 A 001=90. 



