136 CRYSTALLOGRAPHY OF HEMOGLOBIN IN RELATION 



even in the same preparation, and by varying the method of preparation 

 many forms of crystals may be obtained from a given species. Different 

 forms of crystals have been obtained from the blood of different vessels 

 of the same species or the same individual. Different observers have pro- 

 duced quite different crystals from the blood of a given species, some of 

 these closely resembling or seemingly identical with those obtained from the 

 blood of other species. There can not, therefore, be any one form of crystal 

 that is characteristic of a given species. Preyer himself, while recognizing 

 that crystallographic differences exist between the hemoglobins of different 

 species, states that little importance is to be attached to statements on the 

 crystallographic dissimilarities of the hemoglobin of different species, 

 because neither is the same method of crystallization used nor is the blood 

 always capable of being compared. He might have added, that in very 

 few cases have the crystallographic descriptions been at all adequate or even 

 accurate, but this he probably failed to recognize. His statement that all 

 hemoglobins crystallized in the orthorhombic s} r stem excepting that of the 

 squirrel was doubtless taken by many as an argument in favor of the assump- 

 tion of the identity of the blood crystals obtained from different species. 



We thus see that equally expert observers, working with the same data, 

 have arrived at very diverse conclusions. Before attempting to reconcile 

 these conflicting conclusions it will be of advantage to examine certain other 

 observations that have been made on hemoglobin crystals. 



A number of the earlier investigators, including Lehmann, Teichmann, 

 Weir Mitchell, and Bojanowski, and several of the later ones, such as 

 Struve, and Stirling and Brito, have noted that the crystals obtained from 

 the blood may be nearly or quite colorless, or may become so on standing; 

 or, according to several of them, the deep-red crystals may be decolorized 

 by washing them with alcohol, or with alcohol and water, or with other 

 reagents. Thus, Bojanowski states that the blood crystals exposed to the 

 air retain their form, but become paler and paler and finally completely 

 colorless. The addition of sugar or gum produces the same result. Teich- 

 mann had made similar observations on the loss of color of the deep-red 

 crystals. Bojanowski's statement is a fairly accurate description of the 

 paramorphous change of crystals of oxyhemoglobin to metoxyhemoglobin, 

 many examples of which will be found in the records of this research. The 

 color of the crystals of metoxyhemoglobin is very pale as compared with 

 that of oxyhemoglobin, and when the crystals are thin they appear almost 

 colorless. The very strong pleochroism of metoxyhemoglobin makes the 

 crystals appear quite colorless in some positions. Weir Mitchell made 

 similar observations on oxyhemoglobin crystals exposed to the air. The 

 "colorless" crystals retain the form of the original oxyhemoglobin crystals, 

 but after the change they are a different substance, and are in fact pseiido- 

 morphs of the original oxyhemoglobin crystals, and if dissolved and recrys- 

 tallized the form would probably be altered only slight!}^ not sufficiently 

 to be noticed by casual observation. 



From the blood of the raven that had stood exposed to the air for 8 

 days, Bojanowski obtained " crystals which were partly bright yellow and 



