236 CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



the crystals kept well at temperatures under 15 C., but did not form well 

 at 25 C. or higher. At moderate temperatures they showed no tendency 

 to dissolve. They were oxy hemoglobin. In solubility they resemble the 

 crystals of the black rat, being perhaps somewhat more soluble, but they 

 are very much more soluble than the crystals of the white rat or the Nor- 

 way rat. Crystallization was not complete, the mother-liquor remaining 

 quite strongly colored. The crystals in the slides were in good condition 

 a month after the preparations were made. Only one kind of crystal was 

 observed, corresponding to the a-oxyhemoglobin of the Norway rat. 



Oxyhemoglobin of Mus alexandrinus. 



Orthorhombic : Axial ratio a : b : 6 =-0.7829 : 1 : 0.5880. 



Forms observed: Unit prism (110), brachydome (Oil). 



Angles: From the aspects presented by the crystals the prism angle could not be 

 measured; it was assumed as the same as that determined for the Norway rat, 110 A 

 110=76 7'. The only angle that could be measured was the plane angle of the brachy- 

 dome on the prism face; this was, edges 110-011 A 110-OTl =130 19', the average of 

 a number of measurements. From this angle and the assumed prism angle of 76 7' the 

 axial ratio was calculated. The true brachydome angle Oil A Oil could not be observed. 



227 228 



Fios. 227. 228, 229. Miu alexandrinus Oxyhemoglobin. 



Habit tabular on two opposite prism faces and somewhat elongated parallel to the 

 vertical axis (text figure 227) ; the crystal consists of the flattened prism terminated 

 by the flat brachydome. Distorted crystals, in which the two brachydome faces on one 

 side of the prism are alone developed (text figure 228), or crystals with one end so devel- 

 oped and the other showing the two dome faces (text figure 229), are very common; 

 these distorted crystals are rather more common in the crystals of this species than in 

 those of the black rat. There are thus formed four, five, and six-sided plates, the four 

 and five-sided tabular crystals having a decidedly hemimorphic aspect. By shortening 

 of the prism the tabular crystal becomes a hexagonal plate, but owing to the two angles 

 of 130 19' it is not a regular hexagon. The crystals are considerably larger than those 



Flos. 230,231. Mm aleiandrinue Oxyhemoglobin. 



of the black rat in preparations made under the same conditions, indicating that they 

 are more soluble than those of the black rat. Twinning occurs on the flat aspect; two 

 crystals united on the prism face with the orientation that of a twin in the zone of the 

 brachypyramid, which would bevel the dome-prism edge (text figure 230) ; but such 

 twins are very rare. The stellate twin on a pyramid of the unit series is more common, 



