1897 - 98 .] Dr D. F. Harris on Spectroscopy of Hcemoglobin. 207 
preparations in balsam three years old showing crimson crystals 
both from rat and guinea-pig. Such preparations still give the 
two bands of Hb0 2 in the microspectroscope. (I may here men- 
tion that hsemin crystals do not do so.) 
It seems evident that there are two fundamental forms of Hb0 2 
crystals in the rat — (1) the elongated rhomboidal prism ; (2) the 
thin flat plate : if the former tapers at both ends, we have the 
acicular; if only at one end, the clavate. The plate may be a 
regular hexagon, as Halliburton (13) found, so that this form is 
not absolutely confined to squirrels’ blood, or it may be an 
irregular hexagon, a pentagon, or other polygon (size of rat’s- 
regular hexagons is from “002 to “003 mm.). 
I noticed the formation, as it were, of certain of the flat plate 
crystals (regular hexagons included), by the lateral coalescence of 
radially disposed rows of granules, or of acicular or clavate crystals; 
disposed in one plane ; while, after three weeks, I saw certain 
apparently homogeneous crystal-plates breaking up into rows of 
granules, radially disposed, or into radiating acicular or clavate 
crystals. Some plates broke up into radiating feathery forms.* 
In the cases in which the thin flat plate was formed at first as 
such , i.e., quite homogeneously, it did not break up radially, but 
cracked into a number of polygonal areas, like a mosaic. Some of 
these thin flat regular hexagons are after three years quite intact. 
Further, I corroborate Halliburton that the regular hexagons are 
formed near the periphery of the preparation, i.e., where drying 
went on most vigorously — the rapidity of loss of moisture being 
evidently a factor in determining the size and details of form of a 
crystal. 
Guinea-pigs’ blood mixed with balsam sometimes yields some 
very large tetrahedra (“05 mm. side) of a bright crimson colour. 
Occasionally one finds aborted forms — thick triangular plates with 
upward sloping edges (“04 mm. side) — evidently the foundation 
upon which the pyramid was to have been built. Some of these 
thick plates were yellow, not red ; and after three weeks became 
eroded on the edges, which were previously particularly sharply 
cut. 
* This breaking up of crystals into simpler elements I have also seen in 
very old cholesterine crystals. 
