OF THE MARSUPIALIA, EDENTATA, AND SIRENIA. 



179 



The correspondence is probably even more close, for the angle /? of the a-oxyhemo- 

 globin was perhaps 43, as some measurements made it. The prism angles are practically 

 identical. The extinction angles vary 4 and in the same direction as the angle /?. The 

 optical characters are identical. 



fi-CO -hemoglobin of Didelphis virginiana. 



Hexagonal: No axial ratio determinate. 



Forms observed: Prism (1010), base (0001). 



Angles: Prism angle 10TO A 0110 = 60 (120); base to prism 0001 A 1010=90. 



Habit tabular, the crystals consisting of the short prism and base (text figure 70), 

 with the base greatly developed. They occurred sparingly in a few slides, and were not 

 common, as was the case with the /3-oxyhemoglobin crystals. 



The color and absorption spectrum showed them to be 

 CO-hemoglobin, but they were darker than the a-CO-hemo- 

 globin crystals owing to their lack of pleochroism. On the 

 base the crystals show no double refraction or pleochroism, 

 and on edge the pleochroism was practically nothing. On side 

 view they show a very weak double refraction and extinguish 

 straight. On the base in convergent light a very dusky cross 

 of a uniaxial interference figure was observed; the vertical axis is the axis of less elas- 

 ticity, or s > a>, and the optical character is positive. 



Compared with the /3-oxyhemoglobin these crystals are seen to have identical 

 characters, and there is probably no doubt that if the /?-oxyhemoglobin crystals are 

 mimetic twins these are also. The forms of twinning noted for the a-oxyhemoglobin 

 would produce such mimetic forms if the twinning was repeated or polysynthetic. Such 

 twins, with the twin axis lying in the basal pinacoid and normal to the prism-base edge, 

 and the base as the composition face, were apparently observed in the a-CO-hemoglobin 

 along with the type of twin already described. 



The close resemblance of the oxyhemoglobins and the CO-hemoglobins in this 

 species is what might be expected from the other resemblances between these compounds. 

 It will be noted, however, that the reduced hemoglobin varies from either in the incli- 

 nation of the base and in the prism angle. Table 38 shows these differences plainly. 



TABLE 38. Differences of the oxyhemoglobins and CO-hemoglobins in Didelphis virginiana. 



FIG. 70. Didelphis virginiana 

 0-Oxy hemoglobin . 



TASMANIAN DEVIL, Sarcophilus ursinus. Plate 18. 



The specimen was obtained from the National Zoological Park at 

 Washington, District of Columbia, and consisted of about 2 c.c. of oxalated 

 blood preserved in our usual collecting tube. The blood was centrifugal- 

 ized and the corpuscles separated and laked with ether. Preparations 

 were made in the usual manner. The blood crystallized very readily and 

 photographs could be taken within 2 hours of making the preparations. 

 The blood being in good condition, the crystals were oxyhemoglobin, as 

 determined by the spectroscope. 



