324 SUMMARY AND CONCLUSIONS. 



tive systems. Among the antelopes, the blood of the duickerbok, Cepha- 

 lophus grimmi, gives two forms of oxyhemoglobin, a-oxyhemoglobin which 

 crystallizes in the tetragonal system, and /^-oxyhemoglobin which crystal- 

 lizes in the hexagonal system. 



The marsupials show the same tendency to form several kinds of 

 hemoglobins. Thus the opossum blood furnished an a-oxyhemoglobin, 

 monoclinic, and a /^-oxyhemoglobin, hexagonal or pseudo-hexagonal. The 

 CO-hemoglobin of the opossum is also dimorphous, crystallizing in the 

 monoclinic and hexagonal systems in forms analogous to the oxyhemoglo- 

 bin. The oxyhemoglobin of the Tasmanian wolf, Thylacynus cynocephalus, 

 is dimorphous, the a-oxyhemoglobin is monoclinic, and the /3-oxyhemoglo- 

 bin-is isometric. Other examples of dimorphism or trimorphism of the 

 hemoglobins will be found in the detailed descriptions of species. The occur- 

 rence of these different kinds of crystals of these substances in the same 

 species demonstrates the possibility of the presence normally of two or more 

 kinds of oxyhemoglobin, reduced hemoglobin, etc., in the same blood. 



It has been generally stated that the oxyhemoglobin, reduced hemo- 

 globin, methemoglobin, etc., of any given species crystallize in the same 

 form, but a glance at the tables of the crystallographic characters of the 

 different species examined will show that this is not always the case. The 

 mistake has arisen in several ways. In the first place, crystals of oxyhemo- 

 globin may be converted by paramorphous change into metoxyhemoglobin 

 (which has generally been described as methemoglobin) and into reduced 

 hemoglobin, without alteration of angles. Such altered crystals are anal- 

 ogous to the paramorphs and pseudomorphs observed in minerals. Then 

 the above-mentioned confounding of metoxyhemoglobin with methemo- 

 globin (both of which substances we have observed in the same species) 

 has led to a further confusion. The metoxyhemoglobin of a given species 

 generally crystallizes in forms that are near those observed in the oxyhemo- 

 globin, the angular differences being such that exact measurements of the 

 angles are often necessary to show the differences in form of the two sub- 

 stances; but often, while the angles may approach each other in the two 

 substances, the optical characters may be quite different. 



That the oxyhemoglobin, reduced hemoglobin, metoxyhemoglobin, 

 and methemoglobin in one species may differ in crystallization can be illus- 

 trated by many examples from the bloods examined. But in order that 

 the crystals shall differ in form, they must not be paramorphs, but must 

 be crystallized de novo from solution. These four substances were observed 

 in the blood of the shad, Alosa sapidissima, with the following characters: 

 Oxyhemoglobin, monoclinic, axial ratio 1.804 : 1 : 6, /3 = 68, and an extinc- 

 tion angle a A a =6; metoxyhemoglobin, monoclinic, axial ratio 1.786 : 1 : c, 

 (3=70, with an extinction angle of a A a = 10; reduced hemoglobin, mono- 

 clinic, axial ratio 1.786 : 1 : c, j3 = 70, as in the metoxyhemoglobin, but 

 with an extinction angle a A a = 14; methemoglobin, hexagonal, axial ratio 

 not determinable, but with straight extinction. 



When the CO-hemoglobin was examined it generally was ' found to 

 approach the oxyhemoglobin in its crystallographic characters, but differ- 

 ences were usually to be noted. For example, in the horse the oxyhemo- 



