196 



CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE UNGULATES. 



Pleochroism is readily observed; a pale pinkish, b rather moderately deep red, 

 c deep red, 6 and c being nearly equal. Double refraction is not very strong; extinction 

 is straight in all aspects. The orientation of the elasticity axes is a = 6, b=b, c = a. Axial 

 plane is the brachypinacoid, the acute bisectrix Bx a = a; hence the optical character 

 is negative. Traces of the brushes of an interference figure show on looking along c, and 

 the separation of the axes is hence probably wide. 



fi-Oxyhemoglobin of Mule. 



Monoclinic: Axial ratio a : 6 : 6 = 1.7147 : 1 : t; fl = 72. 



Forms observed: Unit prism (110), orthoprism (210) (?), orthopinacoid (100), 

 base (001). 



Angles: Prism angle, traces of prism on base, edges 110-001 A lTO-001 =60 30'; 

 prism edge to base, edge 110-110 A 001=72=/?. 



125 



130 



FIGS. 124-133u. Mule 3-Oxyhemoglobin. 



Habit tabular on the base, the crystal consisting of the basal pinacoid cut by the 

 prism (text figures 124 and 125) and sometimes (but rarely) showing the orthopinacoid 

 (100) and a very small prism face which is probably (210) (text figure 126). The crystals 

 are normally twinned on an axis lying in the base and normal to a prism-base edge as in 

 the horse, etc. In this twin (text figure 127), the composition face is usually the base, 

 but may also be the plane normal to the base that includes the common prism-base edge 

 (see plate 28, fig. 164). This produces a twin, which, owing to the elongation of the 

 crystals along the common prism-base edge as an axis, closely resembles the common 

 gypsum twin on the orthopinacoid (text figure 128). When considerable oxalate is used, 

 the crystals that appear after the first crop are frequently developed along the vertical 

 axis, until they become equidimcnsional (text figure 129), or even somewhat prismatic 

 in habit. These crystals show the symmetry of the twins better than the simple plates. 

 In some of these, a sort of parallel growth on the base is indicated, with the orientation 

 of the a axes of both members of the group such that both lie in the same vertical plane 

 of symmetry (text figure 130) ; and also, in other cases, the group in the reverse position, 

 forming a Manebach twin (text figure 131). But, in general, the type of twinning above 



