Januaey 27, 1911] 



SCIENCE 



149 



the various organs of a certain species have in 

 common a " species " group that is character- 

 istic for one species and differentiates it from 

 nearly related species. By these " biological " 

 methods it had also been found that the con- 

 stitution of these groups of proteid is more 

 similar in nearly related than in more dis- 

 tantly related species, and several investiga- 

 tors, especially Osborne and Abderhalden, had 

 previously taken up the problem of the chem- 

 ical characterization of species differences by 

 the methods of analytical chemistry. 



The vrork of Eeichert and Brown differs, 

 however, in some important aspects from the 

 previous investigations (differentiation by 

 biological tests). While in the latter the 

 substances compared with each other were 

 usually chemically not well defined, Eeichert 

 and Brown worked with a definite chemical 

 substance, the hemoglobin. By the method of 

 crystallization it is, moreover, possible to de- 

 tect differences in chemical constitution which 

 are at present not accessible to ordinary chem- 

 ical analysis and in this way it is possible to 

 differentiate between species so nearly re- 

 lated, that even by means of the so-called bio- 

 logical tests the differentiation is accom- 

 plished only with great difficulty. 



After a study of Eeichert and Brown's work 

 little doubt is left in the mind of the reader 

 in regard to the usually close relationship of 

 the crystals of the species belonging to one 

 genus or occasionally even of the great simi- 

 larity of the crystals of two nearly related 

 genera; it seems, however, not yet established 

 that a general parallelism exists between the 

 true relationship of the various orders and 

 classes of animals and the character of their 

 hemoglobin crystals. 



It might furthermore be questioned in those 

 cases in which a divergence seems to exist be- 

 tween the ordinary classification and the 

 results of the crystallographic studies, whether 

 the latter should be accepted unhesitatingly. 

 It rather seems that in such cases of doubt a 

 comparative study by the crystallographic, 

 and by the so-called biological tests should be 

 used to confirm the former. This would be 

 especially desirable in view of the great 



lability of the hemoglobin molecule which the 

 authors themselves repeatedly emphasize. 

 We might, e. g., question whether the differ- 

 ent kinds of crystals of oxyhemoglobin found 

 occasionally in the same blood might not be 

 the result of certain secondary chemical 

 changes in the hemoglobin molecule. In this 

 connection it is of interest that in a recent 

 publication Offringa states, that if the 

 crystals of hemoglobin of the horse are pre- 

 pared without the addition of any salt 

 (Eeichert and Brown made use of oxalates in 

 their work), only one kind of crystals is ob- 

 tained. 



In the work of Eeichert and Brown, as well 

 as in the more recent literature generally, the 

 term " specific " is frequently encountered, 

 and it is apparently supposed to have a defi- 

 nite biochemical meaning. A more searching 

 analysis, however, reveals the fact that this 

 term includes three different relationships be- 

 tween substances, and a clear distinction be- 

 tween these appears to be very desirable. 

 Several years ago the reviewer described a 

 class of substances which he designated as 

 specifically adapted; these are substances co- 

 existing in the same organism and showing 

 functional relations to each other. In other 

 cases the term " specific " merely indicates a 

 character of a certain species by which it 

 differs from other species, without any 

 parallelism existing between this character- 

 istic and the zoological classification. In a 

 third class of specific characters such a re- 

 lationship exists, and this third kind of 

 specificity might appropriately be called 

 " generic specificity." With the latter, we 

 have principally to deal in the work of 

 Eeichert and Brown. 



The work of these authors includes also a 

 consideration of the general characters of 

 hemoglobins as well as a summary of other 

 differences which have been found in the 

 blood of different species by previous investi- 

 gators. With some opinions expressed in this 

 part of the book issue might, perhaps, be 

 taken, as for instance, in regard to the low 

 estimate of the physiological importance of 

 iron as a constituent of hemoglobin; a view 



