230 CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



WHITE RAT, ALBINO OF Mus norvegicus (Mus norvegicus var. albus Hatai). Plate 53. 



A number of specimens were examined at different times, the living 

 animals being bled in the laboratory. The general method of preparation 

 was to bleed the animal into oxalate, lake the whole blood with ether, and 

 centrifugalize. From the clear solution slide preparations were made as 

 usual. Modifications of the method above described, using corpuscles and 

 adding variable amounts of plasma in excess of the normal, gave about the 

 same results as the preparations of the whole blood. The blood crystallizes 

 very readily, so much so that the crystals are usually small unless methods 

 of preparation are used that retard crystallization. Being small, they show 

 but little color; the crystals examined were, in each case, determined to be 

 oxyhemoglobin by the microspectroscope. A superficial examination 

 shows that the crystals are of several habits, and they look as though 

 they were of different systems. Careful study shows, however, that they 

 are all of the same crystallization, although one type, a hexagonal plate, 

 seems to be sometimes a mimetic twin of the normal crystals. 



Oxyhemoglobin of Albino of Mus norvegicus. 



Orthorhombic : The axial ratio was calculated from the traces of the macrodome 

 on the prism, assuming the same prism as in Mus norvegicus; it is a : 6 : 6 =0.7829 : 

 1 : 0.7332. 



Forms observed: Unit prism (110), brachydome (101). 



Angles: The only angles that can ordinarily be observed are the plane angles 

 between the edges produced by a prism face intersecting the two brachydome faces, 

 that is edges 110-011 A 110-OTl =120. The half of this angle can also often be meas- 

 ured, and it is 60 actual angle. In twins of the stellate shape, the edges are inclined to 

 each other at 60. As this dome angle on the prism is the same as in Mus norvegicus, 

 the true dome angle Oil A Oil is assumed to be the same also, 72 30', which makes 

 the prism angle 110 A 1TO=76 7'. 



Habit thin tabular, elongated along the vertical axis and the crystal tabular on 

 two opposite faces of the unit prism (110), the end being formed by the faces of the 

 brachydome (text figure 207). The tabular crystals are thus roughly six-sided with 

 two sides longer than the other four. Some symmetrically developed crystals of the 

 combination of prism and brachydome were seen (text figure 208), but they were 

 always very small. Generally when the prism faces were equally developed, which 

 occasionally happened, the dome faces were unsymmetrical, two opposite faces being 

 larger and the other two smaller, but usually two opposite prism faces were larger, 

 making the tabular crystal, and the other two prism faces were smaller (text figure 

 209). The prism is very nearly square, although evidently not quite so; but no cross- 

 sections of it could be obtained for measurement. The ratio given a : b =0.7829 : 1 

 was calculated by assuming the same prism that was determined for the Norway rat 

 crystal, which gave the same plane angle of macrodome on prism face as in this albino 

 variety. The usual crystals are hence like vertical sections of the prism, parallel 

 to one pair of faces; and, as the section approaches the exterior of the symmetrical 

 crystal, the outline of the section becomes nearly four-sided; whereas a median section 

 is nearly regularly six-sided, with four short and two long sides. This flattening of 

 the prism produces the tabular effect, and there is, therefore, a flat view and an 

 edge view of each crystal possible. The above descriptions refer to the flat view, but 

 the edge view is quite analogous. The crystals twin by growing together on a prism 

 face either on the flat or on the edge aspect, with the prism edges of the individuals of 

 the trilling (which it usually is), at almost exactly 60 with each other. When this is 

 on the flat aspect the crystals seem to pile up on each other at the 60 angle (text figure 



