148 



SCIENCE 



[N. S. Vol. XXXIII. No. 839 



of the results that are of interest to the biol- 

 ogist.' 



Hemoglobin, the coloring matter of the 

 blood, which in vertebrates is contained in the 

 blood corpuscles, and which is a combination 

 of a proteid, the globin, with the coloring mat- 

 ter proper, the hematin, can more or less read- 

 ily be obtained in the form of crystals. Many 

 investigators have studied the conditions 

 under which these crystals form and some of 

 their characters in different species of ani- 

 mals. The work of Keichert and Brown is, 

 however, by far the most thorough and ex- 

 tensive investigation which has so far been 

 published, and on the basis of their careful 

 studies the authors arrive at broad biological 

 conclusions, which will be of great interest to 

 a wide circle of scientists. 



The results obtained leave no doubt that 

 the crystals of the hemoglobin of different 

 species are not identical, and the work, more- 

 over, raises problems which have not been con- 

 sidered by previous investigators. The au- 

 thors show that not only do the crystals of 

 different species of animals differ, but also 

 that this difference is a graded one, corre- 

 sponding to the position which the various 

 species occupy in the zoological system. As 

 the crystals of nearly related species resemble 

 each other more closely than those of more 

 distantly related species, the character of the 

 crystals permits us to decide, within certain 

 limits, how nearly related to each other ani- 

 mals are. Furthermore, inasmuch as crystal- 

 lographic characters are the expression of 

 chemical constitution, we may conclude that 



^ The reviewer consulted two experts in crystal- 

 lography in regard to the soundness of the crys- 

 tallographic basis of the work, and he may be 

 permitted to cite here a few sentences: 



Professor Edward H. Kraus, of the University 

 of Michigan, states : " From the crystallographic 

 standpoint. Professor A. P. Brown has done a 

 remarkable piece of work which is deserving of 

 highest credit." 



Dr. J. E. Pogue, of the Smithsonian Institu- 

 tion : " The actual crystallographic and optical 

 details are apparently determined with skill and 

 accuracy. The photomicrographs are excellent, 

 and the line drawings good." 



the hemoglobin of various species shows 

 gradations in its chemical constitution cor- 

 responding to the close or more distant rela- 

 tionship of the species. We may also assume 

 that gradations parallel to those shown by the 

 crystals of hemoglobin exist in the other pro- 

 teins. Thus we have a means of testing by 

 crystallography the classification of animals, 

 which at present is based almost entirely on 

 morphological characters. 



The comparative study of the crystals of 

 hemoglobin by the authors confirms, on the 

 whole, the correctness of the classification gen- 

 erally adopted by zoologists, but there are cer- 

 tain instances in which the authors believe 

 that their findings suggest a revision. To 

 cite two examples: (1) It is ordinarily as- 

 sumed that the white rat is an albino of the 

 black rat; the crystallographic examination of 

 the various species of rats shows, however, 

 that the white rat is closely related to the 

 brown or Norway rat, while the black, or 

 Alexandrine rats are more nearly related to 

 each other. (2) The crystals of hemoglobin 

 from the brown bat show a considerable re- 

 semblance to the crystals of hemoglobin of 

 Papio, which belongs to the primates. This 

 agrees with the view of some zoologists, ac- 

 cording to which the bats are related to the 

 primates, although, on the other hand, the 

 crystals of the fruit bat do not show this re- 

 semblance to those of Papio. 



On the whole, the main results of Eeichert 

 and Brown harmonize very well with our gen- 

 eral biological conceptions of the graded re- 

 lationship of differences in the chemical con- 

 stitution of proteid substances, a conception 

 mainly founded upon the results obtained 

 through the application of the so-called bio- 

 logical tests (precipitin, anaphylaxis, comple- 

 ment fixation reactions), and especially are the 

 conclusions of these authors in good agree- 

 ment with the results of experiments in which 

 watery extracts of erythrocytes have been 

 used as an antigen and in which the erythro- 

 precipitins obtained were shown to be specific 

 for the antigens of the various species which 

 had been employed. These studies have defi- 

 nitely proved that the proteid substances Irom 



