222 



CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



acting like a hexagonal crystal; but on edge the pleochroism is noticeable, the color 

 being deeper normal to the plate than parallel to it. On the base the crystal is nearly 

 singly refracting; but by use of the quartz wedge it is seen to be very weakly doubly 

 refracting; on edge the double refraction is easily seen, and extinction is parallel with 

 the base. In convergent light, a uniaxial cross shows in most aspects; but on revolution 

 the brushes open slightly and the crystal is as strongly biaxial as some of the biotite 

 micas. The orientation of the elasticity is a = c, b=a, c=b. The macropinacoid is the 

 plane of the optic axes and the acute bisectrix Bx a = a. The optical character is hence 

 negative. 



FLYING-SQUIRREL, Sciuropterus volans. Plate 47. 



Blood was obtained from the living animal, oxalated, ether-laked, 

 and centrifugalized, and the slide preparations made as usual. Crystal- 

 lization begins as soon as the blood is laked, and proceeds with great rapid- 

 ity, so that the preparations are soon full of minute scales or tabular crystals. 

 To retard the formation of the crystals somewhat, and permit them to grow 

 to a larger size, some preparations were made by diluting the blood with 

 about 3 times its volume of the blood plasma; but, even with this dilution, 

 the crystals begin to form immediately upon laking the corpuscles. They 

 are always small, much smaller than in other species of squirrels, but other- 

 wise resemble those formed in the squirrel bloods in general. They were 

 oxyhemoglobin, as determined by the microspectroscope. 



Oxyhemoglobin of Sciuropterus volans. 



Hexagonal. No axial ratio determinable. 

 Forms observed: Unit prism (1010), 

 base (0001). 



Angles: Prism angle 60 (normals) ; crys- 

 tals are so thin that prism to base could 

 () not be measured with any exactness, but it 

 appears to be 90. 



Habit very thin tabular on the base 

 (text figure 188), minute hexagonal scales or 

 plates, with very little color, owing to their 

 being so thin. They develop in enormous 

 191 numbers, the slides becoming completely 

 filled with them. They generally occur 

 singly or in irregular groups, but a twin on 

 a pyramid of the second order seems to 

 occur, interpenetrant and of the same general form as the tridymite twin (text figure 189). 

 The crystals are very faintly colored, when seen on the flat, but on edge have the 

 red color of oxyhemoglobin, and show pleochroism; a> deep red, very pale red. On the 

 flat, the crystals are singly refracting; on edge they polarize, but not strongly. The 

 direction of the vertical axis or of the optic axis s is the direction of greater elasticity; 

 hence u> > , and the crystals arc negative. 



GROUND-SQUIRREL OR HACKEE, Tamias striatus. Plate 48. 



The specimen was purchased from a collector in eastern Pennsylvania. 

 The animal was bled into oxalate, the blood laked with ether and centrif- 

 ugalized, and slide preparations made in the usual manner. The blood 

 crystallized readily at a temperature of 22 C. The crystals are quite insol- 



190 



Flos. 188. 189. Sciuropterug volans Oxyhemoglobin. 

 Flos. 190, 191. Tamias striatu* Oxyhemoglobin. 



