178 



CRYSTALLOGRAPHY OF THE HEMOGLOBINS 



The twinning in some cases, as seen in edge view, seems to be perhaps of the Mane- 

 bach type, and the two overlapping and crossing plates as seen in the a-oxyhemoglobin 

 (plate 17, fig. 100) are rarely seen. But the type of twinning described above appears to 

 be the normal type. On the flat in some cases the extinction did not seem to be quite 

 symmetrical, but if the crystals are triclinic they must approach the monoclinic very 

 closely, within a degree or two. The form was symmetrically monoclinic. 



CARBON-MONOXIDE HEMOGLOBIN OF OPOSSUM. 



(Dimorphous: a-CO-hemoglobin, monoclinic; /3-CO-hemoglobin, hexagonal or 



pseudo-hexagonal.) 



The stale blood was treated by regenerating with oxygen as above de- 

 scribed, and then shaking with illuminating gas (water-gas) for 2 hours. 

 After etherizing and centrifugalizing for 3 hours granular matter (stromata 

 of corpuscles?) still remained suspended in the solution. The slides were 

 prepared as usual. Two forms of crystals developed, at first the mono- 

 clinic a-CO-hemoglobin and later the hexagonal plates of the /3-CO- 

 hemoglobin. 



a-CO-hemoglobin of Didelphis virginiana. 



Monoclinic: Axial ratio a : b : t =1.804 : I : 6; /?=41. 



Forms observed: Prism (110), base (001), clinopinacoid 6 (010), positive orthodome 

 (101). 



Angles: Prism angle, traces on the base of 110 A 1TO=5S; prism edge to base, 

 edge 110-110 A 001=/?=41; base to clinopinacoid 001 A 010 = 90. 



Habit thin, tabular, rhombic plates consisting of the base (001) with a very short 

 prism (110) (text figures 68 and 69). The crystals occur singly or twinned, but not in 

 parallel growth as in the a-oxyhemoglobin to any considerable extent. Twins are rare, 

 but a type with the twin axis in the basal plane and at 45 to the crystal axes, the twin- 

 ning plane being normal to the base, and the composition face being the base, was appar- 

 ently observed in several cases. In this form of twin, which somewhat resembles the one in 

 which the arrangement is similar but the twinning axis the normal to the prism-base edge, 

 the axis of a in one member of the twin falls in line with the axis of 6 in the other member. 



The crystals show the usual CO-hemoglobin color and spectrum, and they are 

 rather strongly pleochroic. The pleochroism is as follows: a pale rose, nearly colorless, 

 B deep red, c very deep blood-red. The pale rose color of a is in marked contrast with 

 the usual yellow or reddish-yellow of a in the oxyhemoglobin crystals. The extinction 

 is symmetrical on the base and oblique on the clinopinacoid aspect; the extinction 

 angle is 13. The axial plane is the plane of symmetry and the orientation of the elas- 

 ticity axes is a A a =13 in the obtuse angle, extinction angle; b = 6; c A i=36 in 

 the obtuse angle. On the base the biaxial interference figure is seen with somewhat 

 unsymmetrical arrangement and the brushes widely separated. The acute bisectrix 

 emerges at an angle of 13 with the normal to the base and is the axis of least elasticity, 

 or Bx a =c, and the optical character is positive. On all sections in the zone of (OOl)-(lOO) 

 the extinction is straight. 



Compared with a-oxyhemoglobin, the characters of this a-CO-hemoglobin are shown in 

 table 37. 



TABLE 37. Comparison of characters of a-oxyhemoglobin and 

 a-CO-hemoglobin of Didelphis virginiana. 



