52 



SCIENCE 



[N. S. Vol. XXXVI. No. 915 



Dr. Ernest Anderson, research instructor 

 in chemistry at the University of Chicago 

 since 1909, has heen appointed assistant pro- 

 fessor of general and physical chemistry at 

 the Massachusetts Agricultural College, Am- 

 herst, Mass. 



James A. Gibson, instructor in analytical 

 chemistry at the University of Missouri, has 

 heen promoted to he assistant professor. 



Dr. Geo. I. Adams has been appointed pro- 

 fessor of geology in the Pei Tang University 

 at Tientsin, China, and sailed from San Fran- 

 cisco on July 12. 



Dr. E. E. Glynn has heen appointed to the 

 George Holt professorship of pathology at 

 Liverpool, vacant by the death of Sir Eubert 

 Boyce. Dr. Glynn has for some years held the 

 post of lecturer in clinical pathology in the 

 university. 



DISCUSSION AND COESSSPONDENCE 

 THE MISUSE OF THE TERM " MELANIN " 



Inasmuch as there has recently been a plea 

 for a more exact nomenclature in genetics, it 

 may not be amiss to ask for a more exact 

 terminology in some divisions of bio-chem- 

 istry. It is but natural that we should think 

 of a substance in the terms of its most promi- 

 nent trait, and that whenever we see that trait 

 we should associate it with the substance. It 

 has thus come to pass that all substances which 

 are dark in color and presumably " indestruct- 

 ible " have been termed " melanins." This 

 terminology has nothing to commend it and 

 it often leads to great confusion. To one who 

 has been endeavoring to arrange the literature 

 of the animal pigments the misuse of the term 

 " melanin " has caused an immense amount of 

 unnecessary reading. 



All bio-chemical text-books define melanin 

 in more or less the same language "amorphous 

 black or brown pigments . . . which occur in 

 the skin, hair, epithelium cells of the retina, 

 in certain pathological formations, and in 

 blood and urine in disease." ' 



' Hammarstein-Mandel, ' ' Text-book of Physio- 

 logical Chemistry," Wiley & Sons, 1911, p. 792. 



Among those who do not use the term 

 " melanin " in its true meaning are a large 

 number of chemists. In nearly every chem- 

 ical journal we may find in the tables of the 

 decomposition products of protein hydrolysis, 

 a certain amount of " melanin " or " mel- 

 anin nitrogen." It has long been known that 

 when proteins are heated with mineral acids a 

 black residue is produced which is insoluble in 

 mineral acids, and iecause it is hlach it has 

 been called " melanin." It may, or it may 

 not, be related to the true melanin ; there is at 

 present absolutely no proof on either side; 

 hut until it is shown to he related to the 

 melanins in more ways than color or soluhility, 

 it should not he confused with the true animal 

 pigments. Whenever it is shown that the 

 structure of the molecule of these products is 

 essentially the same as that of the melanins 

 then, and not until then, should they be classed 

 with the melanins. In order to prevent the 

 confusion which arises from this terminology 

 I propose that we substitute for the "melanin" 

 and " melanin nitrogen " of protein hydrolysis 

 the terms proposed by Osborne, " humin " or 

 " humin nitrogen." 



There are some chemists and many biolo- 

 gists who contend that the production of this 

 black humin by the acid hydrolysis of proteins, 

 indicates that the true melanins have an origin 

 in the proteins. There is no evidence except- 

 ing the fact that humins are black and look 

 like melanins. Cane sugar, when boiled with 

 hydrochloric acid produces black humins, 

 which are indistinguishable, except for the 

 absence of nitrogen, from the humins of pro- 

 tein decomposition. Indeed, many of the pro- 

 tein humins may originate in the carbohydrate 

 groups which some proteins carry. In all 

 probability the formation of humins from pro- 

 teins is the same sort of a reaction as the 

 formation of the black products from sugar 

 (i. e., dehydration), and in the latter case 

 there can be no doubt that the product is not 

 a melanin. 



Piettre' and myself have isolated pigments 



= C. B. Acad. Sci., 153, p. 782. 



" J. Biol. CTiem., 8, p. 341 ; Biochem. Bull., 1, 

 p. 207; Bull. Soc. Chim. (4), 11, p. 498. 



