OF THE CATS AND CIVETS. 



293 



with any certainty. With them appeared groups of hemoglobin crystals growing in 

 arborescent forms and in parallel growths (see plate 88, fig. 527), evidently the two 

 vertical pinacoids (100) and (010), terminated by the macrodome (301) (text figure 

 338), sometimes with only one plane of the brachydome (Oil) developed and looking 

 quite monoclinic in habit. Later, prismatic crystals of the usual cat-type appeared, 

 showing the macroprism (320) and the brachydome (Oil) (text figure 339); and, 

 from preparations of the corpuscles, generally the unit prism (110) with the same brachy- 

 dome (Oil) (text figure 340). The dimensions of the prismatic crystals varied con- 

 siderably and the ratio of length to thickness ran from 8 : 1 to 30 : 1. From corpuscles 

 alone, without any dilution of the blood this ratio was 5 : 1 to 3 : 1 or even less (see 

 plate 90, fig. 535), and when the square prism was cut by the cover and slide the crystals 

 looked like cubes or rhombohedra (see plate 90, fig. 536). Frequently these crystals 

 become covered with small second-growth crystals, sprouting out in every direction; 

 they are generally proportionately longer, as is usual in the small prismatic crystals. 

 When the longer crystals meet each other, confined in the thin layer of solution between 

 slide and cover, they frequently are opposed or interpenetrate, thus simulating contact 

 and interpenetrant twins ; but most of these are probably only adventitious orientations 

 and not true twins. Two kinds of twinning appeared to occur, however; one on a brachy- 

 dome, probably about (052), which, when interpenetrant (text figure 341), produces a 

 twin like the square staurolite cross; and the other kind of twin apparently on a pyramid, 

 the two parts making an angle with each other of about 72 (text figure 342) like the 

 oblique staurolite cross. Both were ordinarily seen as interpenetrant twins. 



czv 



338 



342 



339 MO 341 



Fins. 338, 339, 340, 341, 342, 343. Felis domeslica Reduced Hemoglobin. 



343 



Pleochroism was very strong in all of the crystals, except when seen in cross-section 

 of the prism, when it was weak. The colors varied with the thickness, but were usually: 

 a pale rose-pink to purplish-lilac or nearly colorless, b various shades of rose-red, paling 

 to rose-pink, c deep rose-red. Extinction was straight, or symmetrical, in all sections. 

 Double refraction is strong. The interference figure is easily seen in convergent light on 

 cross-sections; and the axial angle is evidently large. The orientation of the elasticity 

 axes is a = b, b=a, c =<J. The plane of the optic axes is the macropinacoid (100) ; the acute 

 bisectrix is the axis of least elasticity Bx a =c. The optical character is hence positive. 



As the first-formed crystals of reduced hemoglobin increased in size, they became 

 quite tabular on the brachypinacoid (Oil), and the prism developed on the vertical edge 

 that at first appeared to be occupied by the macropinacoid (100) (text figure 343). 

 These tabular crystals showed a tendency to develop into somewhat radiating groups, 

 growing together in the zone of the brachydome and nearly on the brachypinacoid. The 

 crystals of this type appeared to show more of a purplish color than those of the prismatic 

 type; but this was probably due to the fact that there was less of the oxyhemoglobin 

 solution covering the crystal, than in the case of the prisms, and hence less absorption 

 of the reduced-hemoglobin color by the scarlet oxyhemoglobin solution. 



