GENERAL CRYSTALLOGRAPHIC CHARACTERS. 329 



Angles that run close to these angles given under the column of prism 

 angles, on the basis of 88 36' as the ratio 1:1, are found in the prism or 

 dome angles that are recorded; and practically all of the angles that have 

 been recorded lie near one of these points represented by the simple ratios 

 given in the table. 



A more exact method of comparison would be to compare first the 

 angles of the species of one genus with those of the species of a related 

 genus, and from these derive a similar table of mean angles, which would 

 vary from the above recorded angles somewhat. As far as this has been 

 done, as for the dogs and the cats for instance, it shows a closer corre- 

 spondence of the simple ratios than would be seen by simply taking angles 

 from the recorded angles in the tables of crystallographic characters at 

 random and comparing them with those given in this table, which latter 

 are, of course, only very approximate. 



The fact that practically all angles of the crystals (except those which 

 can not belong in this series, as 60, 90, 70 30') run so close to the com- 

 puted angles for the series, indicates that all of the hemoglobins are mem- 

 bers of an isomorphous series, an isopolymorphous series in fact, and the 

 isomorphism is at least partial if not complete. As will be shown later, the 

 isometric, tetragonal, and hexagonal crystals may be, and probably are in 

 all cases, the mimetic twins of the orthorhombic and monoclinic crystals. 

 These, in turn, are related in the same way by simple ratios with the triclinic 

 hemin,* the angles of which, as we have found them in various species, 

 are also members of the above series of angles as given in the column of 

 prism angles for 88 36'= ratio 1:1. As far as this work of comparing the 

 angles of the crystals from different species, and of different substances 

 from the same species, has gone, it clearly indicates the partial or complete 

 isomorphism of all the hemoglobins, and also their isomorphism with the 

 triclinic hemin. 



Such series, isodimorphous or isotrimorphous at least, are known among 

 minerals. The Pyroxene-Amphibole group is such a one, in which ortho- 

 rhombic, monoclinic, and triclinic minerals are found in two series which 

 are related to each other by the simple ratio of 1:2; that is, calling the 

 pyroxene ratio 1:1, then the amphibole ratio becomes 1 : 2. These minerals 

 vary widely in chemical composition, and some are very complex while 

 others are simple, but all may be related by this simple ratio, and all have 

 substantially the same axial ratio. It is in this sense that the hemoglobins 

 may be said to be isomorphous. 



Mimesie, and the angles of 60 and 90 in the crystals: 



It was stated above that crystals of the hemoglobins showing the 

 angles 90, 60, etc., that did not fall into this table of angles, could still be 

 seen to be related to the main series by considering that the angles might 



* During the past two years we have devised methods for preparing relatively large crystals of hemin, 

 and we have examined the hemins of a number of species of animals and measured the crystals, of which 

 we have about 350 negatives. From these records, the above conclusions as to the crystallographic rela- 

 tions of the hemoglobins and hemin have been arrived at. We are now engaged in an active study of hemins 

 and expect to announce the results in the near future. 



