282 



CRYSTALLOGRAPHY OF THE HEMOGLOBINS 



While frequently of quite a different shape from the crystals of oxyhemo- 

 globin, a comparison of the axial ratios will show that the oxyhemoglobin 

 and the reduced hemoglobin must have nearly the same form of structure. 

 The prism angle that develops in the reduced hemoglobin crystals is usually 

 about 88 to 89; this angle also appears in the tabular crystals of oxy- 

 hemoglobin in some cases. The macrodome is usually present in the reduced 

 hemoglobin crystals, and can always be calculated when the complete axial 

 ratio is determined; it runs from 41 30' to 45 in the different species. 

 The following table shows the crystallographic characters of the reduced 

 hemoglobins of the cats: 



TABLE 45. Crystallographic characters of the reduced hemoglobins of the Felidas. 



* Computed. 



A glance at the above table will show that the data for the reduced 

 hemoglobin for the Old World cats are complete, while those for the New 

 World cats are not. If the oxyhemoglobins were compared, the reverse 

 would be found to be the case; the data for the oxyhemoglobin crystals 

 of the Old World cats would be incomplete while that for the New World 

 cats would be complete. The two species of Lynx gave reduced hemoglobin 

 crystals that varied more from each other than they did from the species 

 of the genus Felis proper. This would indicate that, so far as the reduced 

 hemoglobin is concerned, they belong strictly in the genus Felis. 



As the prism angle approaches 90 in the normal unit crystals, twinning, 

 especially mimetic twinning, produces forms that appear to be tetragonal; 

 examples of this probable mimetic twinning are to be found in the oxy- 

 hemoglobin of Felis bengalensis and the reduced hemoglobin of Lynx cana- 

 densis. The more obtuse prism (430) that was frequently observed, has an 

 angle that ranges from 75 to near 72 and thus it approaches the angle of 

 the octahedron; from this are probably developed the isotropic forms 

 with isometric, or pseudo-isometric, development that were seen in the 

 ^-oxyhemoglobin of the jaguar, Felis onca, and the /3-oxyhemoglobin of the 

 puma, Felis concolor. 



The crystals from the blood of the civet examined (Arctictis binturong) 

 did not show the prism, and the terminations were wanting. No axial 

 ratio could be obtained, therefore, for comparison with the cats; and while, 

 like the cats, it is Orthorhombic and positive, it can not be stated that the 

 crystals resemble those of any of the cats examined. 



