262 



CRYSTALLOGRAPHY OF THE HEMOGLOBINS OF THE 



a rather dusky interference figure was observed, showing one brush of the biaxial figure, 

 with traces of the other brush in certain positions. The bisectrix of the optic axes is 

 evidently the axis of greatest elasticity Bx a = a, and the optical character is hence 

 negative. 



SLOTH BEAR, Melursus ursinus. Plates 71 and 72. 



The specimen was received from the Philadelphia Zoological Gardens 

 and was in a very putrid condition. The blood was oxalated, laked with 

 ether, and centrifugalized to obtain the clear solution from which the slide 

 preparations were made. The blood crystallized readily at room tempera- 

 ture, and the crystals were fairly permanent. These first crystals were 

 frequently, but not always, twinned, as was the case with the crystals from 

 the bloods of other bears examined. As in other cases, too, a second crop 

 of crystals formed that were more perfect than those of the first crop; 

 and these were not so frequently twinned. The crystals, especially those of 

 the second crop, kept well and did not dissolve in the solution. They were 

 of the monoclinic sphenoidal class (tartaric-acid type) as in the other bears, 

 but occasionally a slide would contain a few crystals which appeared to be 

 of more symmetrical character. They all appeared to be oxyhemoglobin. 



Oxyhernoglobin of Melursus ursinus. 



Monoclinic hemimorphic, monoclinic sphenoidal (tar- 

 taric-acid type): Axial ratio a : b : 6 =1.2857 : 1 : 1.49S; 

 /? = 6840' (calculated). 



Forms observed: Unit pyramid (Til), unit prism 

 (1TO), orthopinacoid (100), orthodome (101), base (001); 

 in twins, prism (230). 



Angles: Traces of unit prism or unit pyramid on the 

 base, angle of the edges 110-001 A 1TT-001=75 35'; 

 prism to base TlO A 001=77, unit pyramid to base 

 Til A 001 =48 15'. 



Habit thin tabular on the base, the bounding planes 

 being on one end of the ortho-axis the unit prism (1TO), and 

 on the other end the unit pyramid (Til), with very often 

 the orthopinacoid or an orthodome, (100) or (101), making 

 a six-sided plate (text figures 291 and 292). The first crys- 

 tals to form were frequently the trilling, which appears to 

 be common in the bears, and which is described under the 

 black bear (text figures 286 and 287). But this form of twinning was not so common and 

 characteristic as is the case with the two species of Ursus examined. Single crystals were 

 much more common in this species than these trillings; and the twins were almost absent 

 from the crystals of the second crop. These latter were larger and more perfect than those 

 of the first crystals to form, and they were mainly seen along the cover edge. They grow 

 into groups, sometimes quite arborescent in appearance, and all in parallel growth position; 

 the group elongates along the ortho-axis and the faces of the orthopinacoid are likely to 

 develop prominently in these groups. They usually have the appearance of overlapping, 

 roughly hexagonal plates, the overlapping being where the unit-prism edge grows over the 

 unit-pvramid edge. All sorts of irregular groups are thus produced, the crystals appearing 

 to unite on the base with the orientation the same throughout the entire group. Edge 

 views of these second-crop crystals often give the angles of the unit-prism and unit 

 pyramid on the base in measurable condition. The individual tabular crystals, not in 

 parallel growth, frequently grow together in the zone of the pyramid base in radiating 

 groups as seen on edge; some of these may be in twinned position. 



292 



FIGS. 291, 292. Melursus ursinus 

 Oxyhemoglobin. 



