226 



CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



show. The crystal is very thin so that the a direction is very short. The pleochroism 

 on the flat is b pale yellowish-red, c pale red; or, when very thin, 6 colorless and c pale 

 pink. On edge view the crystal shows probably from 5 to 10 times the thickness seen 

 on the flat, and the colors are deeper; a pale pink, c deep red. On the flat aspect in con- 

 vergent light a pair of dusky brushes of a biaxial interference figure shows; the conjugate 

 axis is the long dimension of the lath c, but the brushes pass out of the field on rotation 

 of the crystal. It seems probable from this that the acute bisectrix of the optic axes 

 Bx a =c, and the optical character is positive. Calling the flat side of the lath the macro- 

 pinacoid, the narrow edge the brachypinacoid and the dome a brachydome, the orienta- 

 tion of the elasticity axes is a=a, b=6, c=<<; and the axial plane is the brachypinacoid. 



ir-Oxyhemoglobin of Marmota monax. 



Monoclinic: Axial ratio a : b : 6 =1.804 : 1 : 6; /? near 90 (?). 

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



Angles: Prism angle 110 A HO =58 (about ) ; the angle /? was not exactly observed, 

 but appears to be near 90. 



193 



Flo. 193. Marmota monax fl-Oxyhemoglobin. FIGS. 194. 195, 196. Marmota monax y-Oxyhsmoglobm. 



Habit thin tabular, consisting of the basal pinacoid, bounded by the unit prism 

 (text figures 194, 195); but the crystals rarely occur singly, they form groups radiating 

 from a center both on edge and on the flat (see plate 50). They occurred sparingly as a 

 second growth in preparations made from whole blood, and appeared to be more soluble 

 than the a and /^-crystals. The prism faces at first were curved, making measurement of 

 the prism angle impossible, but later the crystals became more perfect. Single rhombic 

 plates were rare, but the groups were not all irregular. Twinning is the normal type 

 for these rhombic plates ("horse-type," text figure 196) with the twin axis in the base 

 and normal to a prism-base edge. The composition face is the base. The crystals do 

 not seem to elongate along the common edge so much as is usual in this type of twin, 

 but remain symmetrical rhomboidal plates. 



Pleochroism and absorption are not noticeable on the flat view; the color is bright 

 oxyhcmoglobin red. Double refraction is strong on the basal aspect as also on edge; 

 extinction on the base is symmetrical. On edge the extinction is oblique looking 

 along 6, and straight looking along a; the extinction angle is 11 from the trace of 

 the base. On the basal aspect, in convergent light, a biaxial interference figure is seen, 

 with the brushes unsymmetrically placed with respect to the normal to the base. The 

 orientation of the elasticity axes is a A A about 10, b=b, c A a = 11. The angle /? not 

 being exactly determined, the angle a A <5 is somewhat uncertain. The plane of the 

 optic axes is the plane of symmetry (010) and the acute bisectrix Bx a =a; the optical 

 character is hence negative. 



