152 



CRYSTALLOGRAPHY OF THE HEMOGLOBINS 



From the blood of the shad, therefore, crystals of the following sub- 

 stances were obtained: (1) Oxyhemoglobin, from blood that had been 

 exposed to the air. (2) Metoxyhemoglobin from the fresh blood. (3) 

 Methemoglobin from blood that had been exposed to the air, with (1) or 

 from deoxidized blood, with (4), but not with (2). (4) Reduced hemo- 

 globin * from stale blood that had not been exposed to the air. This was 

 also formed by reduction of (2). 



(1) Oxyhemoglobin of Alosa sapidissima. 



Monoclinic: Axial ratio a : b : (5 = 1.804 : 1 : 6; /? = 68. 



Forms observed: Prism (110) and base (001). 



Angles: On base (001) edges 110-001 A lTO-001 =58; edge of (110-lTO A 001) =/?=68. 



The angles of the plates varied, the acute angle being often not the supplement 

 of the obtuse angle in the same plate, this difference being apparently due to some form 

 of twinning. Thus, the acute angle often ranged up to 62, and some were exactly 60. 

 The obtuse angle was always 120 or over, up to 124 and even 125 in a few cases. But 

 in simple, untwinned crystals the angles of 58 and 122 seemed to be the average. 



FIGS. 4, 5, 6, 7. Alosa aapidiasima Oxyhemoglobin. 



Habit of the crystals (text figures 4 and 5) tabular on the base (001), the prism 

 very short, making the crystal a rhomboidal plate with the plane of symmetry including 

 the long diagonal of the plate. Twins with the base (001) as composition face, Manebach 

 type (text figure 6), also in "homogeneous regular growth" like a twin on the pyramid, 

 but with the two parts uniting on the base (001) and the prism edges (110) and (TlO) 

 in juxtaposition (text figure 7). This twin, very common in all these tabular crystals 

 of the monoclinic system, is called the "horse-type" of twin, and is fully described under 

 Horse (p. 192). Regular growths with methemoglobin formed (heterogeneous regular 

 growths) the methemoglobin crystals, which are hexagonal, forming in symmetrical 

 position on the monoclinic Oxyhemoglobin (text figure 14; see also plate 4, figs. 21, 22, 

 and 23). The twinned crystals of the Oxyhemoglobin with angles of 60 were usually 

 found so overgrown; but this was not always the case, as may be seen by reference to 

 the figures, see plate 4, fig. 24. 



Crystals are strongly pleochroic; a pale yellowish-red, b deep red, c deep red; the 

 colors for light vibrating along b and c are about alike. Axial plane _L to axis b or in the 

 plane of symmetry. Orientation of the elasticity axes is as follows: b=6, aAa=6 

 in the obtuse angle, c A ^ = 16 in the obtuse angle; the extinction angle looking along 

 b is hence 6 from the trace of (001), which is the extinction angle in edge view of the 

 plate, with the long diagonal of the plate normal to the line of sight. On the base, traces 



*The term " reduced hemoglobin," while a misnomer, is nevertheless conventional to express a spe- 

 cific substance. The indiscriminate use of the term ' hemoglobin " to indicate several entirely different 

 bodies necessitates the continued use of the term " reduced hemoglobin " or the adoption of some equally 

 specific substitute. 



