OF THE CATS AND CIVETS. 285 



to change to metoxyheinoglobin, the very long needles of the reduced hemoglobin ap- 

 peared in brush-like tufts; and still later, the relatively enormous crystals noted above. 

 The larger the crystals grow, the more they tend to become flattened by the slide and 

 cover, and, as they usually lie on a prism face, this flattening is generally on a pair of 

 prism faces. The dome angle thus developed, which is a section of the dome faces along 

 the diagonal plane parallel to a prism face, is of course more obtuse than the true angle 

 and in these sections it appears as an angle near 30 (normals) . The crystals appear to 

 twin on the unit pyramid, in contact and interpenetrant twins (fig. 322). 



Pleochroism is very marked ; a pale rose-pink, b deeper rose-pink, c deep carmine- 

 red; the colors of a and b are not far apart. The orientation of the elasticity axes is 

 a =6, 6= a, c=6. On all aspects extinction is straight or symmetrical. In convergent 

 light on cross-sections of the prism the biaxial interference figure can be seen with the 

 brushes widely separated; the angle 2E is about 100 to 105. The plane of the optic 

 axes is the macropinacoid, and the vertical axis is the acute bisectrix; Bx a = (; hence the 

 optical character is positive. 



BENGAL TIGER, Felis tigris. Plates 82 and 83. 



The specimen of blood was received from the Philadelphia Zoological 

 Gardens. After oxalating, the blood was repeatedly frozen and thawed to 

 dissolve the hemoglobin from the corpuscles; finally, upon thawing, a mass 

 of broken crystals was obtained. Water was then added in small amount, 

 the blood warmed to room temperature and centrifugalized. From the clear 

 solution thus obtained the slide preparations were made as usual. Crystals 

 of reduced hemoglobin began to appear very soon after the slides were cov- 

 ered; the crystals formed rapidly, and were at first, when small, very even 

 in size and shape; later, some grew to relatively enormous dimensions, 

 while the others remained small. The crystals are very insoluble, evidently, 

 and remain very sharp and well formed for days, showing no tendency to dis- 

 solve in the plasma. Only crystals of reduced hemoglobin appeared in these 

 slides, the blood being somewhat stale and putrescent, a condition which it 

 probably acquired inside of the animal before the specimen was collected. 



Reduced Hemoglobin of Felis tigris. 



Orthorhombic: Axial ratio a : b : 6 =0.9741 : 1 : 0.3838. 



Forms observed: Unit prism (110), macrodome (101). 



Angles: Prism angle, 110 A 1TO=8830' (normals) (also meas- 

 ured 89, giving axial ratio 0.9827 : 1 : 0.3871) ; macrodome angle, 

 101 A T01=43 (normals). 



Habit short prismatic, elongated along the vertical axis; a nearly 

 square prism (110) cut by a rather flat macrodome (101) (text figure 

 323) ; the ratio of length to thickness of the prism, whether large or 

 small (except the most minute crystals), ranging from 3 : 1 to 2 : 1. In 

 very minute crystals this ratio may rise to 5 : 1, and in very large crys- Fio 3 . 13 Fe!is 

 tals it falls to 3 : 2. In some exceptional cases the ratio was 1 : 2, the tigris Reduced 

 crystal becoming almost tabular on one of the macrodome faces, and 

 hence distorted. But in general the crystals were very symmetrically developed. The 

 usual aspect presented is that of the crystal lying on one prism face and showing the dome 

 in an oblique position. The cross-section of the crystal was also occasionally seen, but 

 generally in a somewhat oblique position. The exact measurement of the prism angle 

 was therefore not easy, and it may vary towards 90 by some half-degree (89 normals). 

 The profile view of the macrodome was seen frequently enough to allow of rather exact 

 measurement. Twins were rare, but an interpenetrant twin on a unit pyramid was 

 apparently seen (compare text figure 322). 



