198 



CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE UNGULATES. 



Flos. 134, 135, 136. Hippopotamui amphibius 

 Oxy hemoglobin. 



until they form a plate, with the bases in contact throughout, and bounded by two long 

 sides of unequal length and two short sides of equal length (see text figure 136, also plate 

 31, fig. 182). This produces an apparently hemimorphic crystal, the axis of hemimor- 

 phism being the twin axis. The twin elongates along the normal to the twin axis or along 

 the common prism edges. The large crystals that developed in the slides, up to 2 mm. 

 or more long, were of this type. The composite character is evident in the large crystals, 



but not so much so in the smaller ones. The 

 more complicated groups appear to be either 

 twins of the above-described type, in polysyn- 

 thetic development, or twins on a pyramid of 

 the unit series (see plate 31, fig. 184, for both 

 types). 



In the crystals that were being dissolved 

 by warming the solution, corrosion planes 

 appeared in the zone of the negative unit pyr- 

 amid. Etching figures also appeared, which 

 seem to show monoclinic symmetry. 



Pleochroism is quite strong, and is very 

 noticeable even in the twins; fl nearly color- 

 less, pale yellowish-red; b moderately deep 

 red, c very deep red. On all sections parallel 

 to axis b the extinction is symmetrical. On 

 side view, looking along 6, it is oblique, with 

 an angle of 20 or more with the edge 010-001. The extinction in the twins described 

 above is variable with the thickness of the members of the twin; it was not often sym- 

 metrical or parallel to the axis, but usually somewhat oblique. In convergent light, 

 an axis is seen to emerge along the short pseudo-trigonal axis of the rhombohedron-like 

 stumpy crystals, showing a single brush, which rotates as the crystal is rotated, and 

 indicates the position of the axial plane. No complete interference figure was observed. 

 The plane of the optic axes lies in the plane of symmetry and the orientation of the elas- 

 ticity axes is as follows: a A a = about 20, in the acute angle; b=b, c A (5=44, in 

 the obtuse angle. Hence, c should be the acute bisectrix and the optical character is 

 positive. 



PECCARY, Dicotyles labiatus. Plate 31. 



The blood was from a young peccary, received from an unrecorded 

 source. The slides were prepared in the usual manner, and the crystals 

 formed soon after the slides were covered; but they began to break down 

 and dissolve, within 4 hours after the preparation was made. They were 

 not very perfect and appeared to be soft and porous. The crystals were 

 oxyhemoglobin. 



Oxy hemoglobin of Dicotyles labiatus. 



Tetragonal: Axial ratio a : 6 =1 : 0.7133. 



Forms observed: Unit pyramid (111), diametral prism (100). 



Angles: The angle of the pole edges of the pyramid was 109. The angle of the 

 prism faces was 90. 



Habit dodccahedral, the combination of the unit pyramid (with angles almost 

 that of the isometric dodecahedron) and the diametral prism giving, when in equilib- 

 rium, crystals that look almost exactly like the isometric form (text figure 137). The 

 development is usually somewhat greater in the direction of the vertical axis, and hence 

 the habit is rather tetragonal in many crystals. But looking down what would be the 

 trigonal axis, if it were isometric, along the normal to (201), the trigonal appearance of 

 the crystal is very pronounced. In fact, the crystals could be taken for isometric, were 

 it not for the polarization character. 



