CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE UNGULATES. 



195 



three individuals; often more, up to six. They frequently form complicated groups. 

 The twinned crystals are generally elongated in the direction of the common edge, as 

 was the case with the /9-oxyhemoglobin. 



Pleochroism rather marked; a pale pink, & deep rose-pink, c very deep rose-red. 

 Extinction is symmetrical on the base and straight on edge, looking along the clino-axis 

 on edge, but looking along the ortho-axis, the extinction angle is about 15 from a. The 

 orientation of the elasticity axes is a A a = 15, in the obtuse angle; &=&; c A 6=7, 

 in the obtuse angle. The plane of the optic axes is the clinopinacoid and on the base in 

 convergent light a biaxial figure is seen, with rather widely separated brushes, showing 

 that the acute bisectrix Bx a = c, and the optical character is positive. The twinning pro- 

 duces apparent optical anomalies; the twins, consisting of three, show a nearly uniaxial 

 figure, and, even with two, the twin sometimes shows two symmetrically placed brushes 

 as though orthorhombic. In the more complicated groups the apparently uniaxial 

 figure is normal, but in all of these the interference cross opens slightly upon revolution 

 of the crystals. 



MULE, Equus asinus (male) X Equus caballus (female). Plates 27-29. 



The blood was obtained fresh and was not oxalated when collected, 

 but defibrinated by beating. Centrifugalized corpuscles were laked and 

 centrifugalized again, preparations being made both with and without 

 oxalate. As with horse, the crystals are dimorphous; and the non-oxa- 

 lated blood crystallized principally in the orthorhombic system, while the 

 oxalated blood crystallizes principally in the monoclinic system; but in 

 each, oxalated and unoxalated, both kinds of crystals appeared in the 

 slides. For example, the corpuscles were laked with a large excess of ether 

 and centrifugalized for a few minutes; preparations from this treatment 

 showed only the orthorhombic crystals at first, but inside of 20 hours the 

 monoclinic plates had developed sparingly, a few to the slide, in large, well- 

 formed crystals. In the same way, the orthorhombic prisms appeared only 

 sparingly in the preparations with a large amount of oxalate. The crystals 

 were all oxy hemoglobin, as determined by the microspectroscope. The 

 two forms are distinguished as a-oxyhemoglobin and /2-oxy hemoglobin. 



a-Oxyhejnoglobin of Mule. 



Orthorhombic: Axial ratio 0.7813 : 

 1 : 0.4198. 



Forms observed: Unit prism (110), 

 macrodome (101). 



Angles: Prism angle 110 A 1TO=76 

 (normals); dome angle 101 A 101=56 30' 

 (normals) . 



Habit prismatic, either long or short, 

 elongated along (110) (text figures 120, 121, 

 and 122), the ratio of the length of the 

 prism to its thickness being about 2 : 1 in 

 the short prisms (text figure 120) and vary- 

 ing up to 20 : 1 in long prisms (text figure 

 121); some are even almost hair-like. The 



prisms grow in irregular groups in the protein ring and along the cover edge, and are also 

 commonly found scattered singly through the slides. The macrodome is usually un- 

 equally developed, one face larger than the other, giving a rather monoclinic aspect to the 

 crystals (text figure 123). The prism faces are also sometimes unequally developed, the 

 prism being flattened on two opposite faces. Twinning was not definitely made out. 



120 



121 



122 



123 



FIQS. 120, 121, 122, 123. Mule o-Oxyhemoglobin. 



