CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE UNGULATES. 



Oxy hemoglobin of Tragulus meminna. 



= 63. 



201 



Monoclinic: Axial ratio a : b : t =1.804 : 1 : 6; /? = 



Forms observed: Unit prism (110), base (001). 



Angles: Traces of prism on the base, edges 110-001 A 110-001=59; true angle 

 110 A 1TO = 64 50' (calculated); prism edge to base, edge 110-110 A 001 = 63 

 (normals) =/?. 



Habit of the single crystals tabular on the base (text figures 142, 143), the plate 

 bounded by the prism faces, generally symmetrical or nearly so; but most of the crystals 

 are twinned with the prism-base edge (110-001) as twin edge and a normal to this edge 

 in the plane of the base as the twin axis (text figures 144 and 145). In these twins the 

 composition face is the base and along one of the prism-base edges, where they unite, 

 there is a reentrant angle, while on the opposite edge there is an ordinary dihedral angle. 

 In these twins (horse-type), which are common in all hemoglobins with angles that 

 approximate 60, the compound crystal in this species is usually elongated along the 

 common edge, and the two crystals overlap each other at the ends of this elongated 

 crystal forming reentrant angles in the outlines of these ends. The twinning is frequently 

 repeated in polysynthetic order; and it is often complicated by parallel growth in one 

 or more of the members of the twin. It does not appear to tend to produce hexagonal 

 forms by twinning on more than one pair of the prism-base edges, however, as is com- 

 monly the case in this kind of twinning. Twinning on the base as twin plane is also 

 found apparently, but it is rare. This twinning seems to tend to make the angle of the 

 plate nearer 60. In some cases the opposite prism-base edges do not appear to be par- 

 allel, due perhaps to a vicinal prism face in one member of the twin; this non-parallelism 

 would tend to average the angles to near 60. 



147 



FIGS. 142, 143, 144, 145. Tragulus meminna Oxyhemoglobin. FIGS. 14ti, 147. TruQulus meminna Reduced Hemoglobin. 



Pleochroism is strong; a is pale yellowish with a reddish tinge, 6 is a blood-red 

 and c is still deeper red than b. Extinction seems to be symmetrical with the sides of 

 the plate; in some cases it appeared a little oblique, but probably the plates were some- 

 what tilted. In twins with symmetrical extinction the angle was about 10 from the 

 prism-base edge. Looking along the symmetry axis, it was about 15 from the trace of 

 the base. The orientation of the elasticity axes is a A a = 15, in the obtuse angle, b=b, 

 c A <! = 12 (about), in the obtuse angle. The axial plane lies in the plane of symmetry; 

 the acute bisectrix of the optic axes is c, hence the optical character is positive. Looking 

 at the crystal normal to the base, in convergent light, the biaxial figure is seen, with one 

 brush constantly in the field, the other passing out on rotating the crystal. The axial 

 angle is hence large. 



The oxyhemoglobin crystals changed to metoxyhemoglobin by paramorphism, 

 without apparent change of form, and they retained their optical orientation and all 

 optical characters, except the pleochroism, which no longer showed any blood-reds, but 

 dull brownish-reds. Otherwise they resembled the normal oxyhemoglobin. This change 

 took place after the reduced-hemoglobin crystals began to appear. 



