18 U. S. BURKAIT OF FISHERIES 



Heinrich Rose, who worked at the instance of Ehrenberg, reports his 

 finc^ings, the conchision from which is that the histrous crystals con- 

 sist of a volatile organic substance. 



Goebel (1S36) introduced a short paper with a reference to news 

 items published in European newspapers (Froriep's Notizen, Decem- 

 ber, 1S85, and lianovrische Zeitung and Berliner Staatszeitung of 

 about the same time) reporting the s(>nsational discovery by ''the 

 well-known chemist, Doctor Du Mesnii, of Wunstorf , " that the 

 metallic luster found on the scales of certain fishes — for example, the 

 carp — is silver. This remarkable conclusion is supported by what 

 purports to be chemical proof (precipitation with ammonium sul- 

 phide). He went so far as to calculate that an ordinary carp will 

 yield about 0.12 gram of silver. Goebel, who reports this interesting 

 but mistaken finding, himself tested Du Mcsnil's conclusion and 

 found no trace of silver, and pointed out that a mere precipitate with 

 ammonium sulphide is not necessarily silver. 



In 1836 appeared a paper by Schnitzlein, who also refers to the 

 work of Du Mesnii and undertakes to test his conclusion. He found, 

 like Goebel, that no silver or other metal was present. He found 

 the crystals to be soluble in dilute acids and alkalies, they burned with 

 a smell of burning horn, were not precipitated with hydrogen or 

 ammonium sulphide, and before the blowpipe yielded no metal. 

 He concluded that the source of the luster was an organic compound 

 of albumen with phosphate of lime. Mathias (1843)^ concluded 

 that the sparkling particles were phosphate of magnesia. 



Von Wittich (1854) was first to prepare the substance in large 

 quantity for chemical examination. He scrubbed the scales in 

 alcohol and separated the sparkling particles, which were disengaged 

 from the membranes and passed into the alcohol. He observed that 

 on igniting the substance a smell of burning horn was given off, and 

 in the ash were found calcium phosphate, ordinary salt, and small 

 quantities of other mineral matters. He concluded that he was 

 dealing with a nitrogenous compound of the inorganic salts that 

 remain on ignition. 



Up to this time it will be seen that even though numerous investi- 

 gators had attacked the problem, no substantial progress had been 

 made in identi!'ying the substance in hand. This does not sp^ak 

 so badly for the chemistry of the time as might at first appear. The 

 real difficulty then, as later, was in getting the substance in pure form 

 for analysis. While the particles make a great showing by virtue 

 of their great luster, they are really so thin as to amount to exceed- 

 ingly little substance. In proportion to volume, they are possessed 

 of great surface on which impurities can accumulate, and it has 

 always been difficult to free them from the large quantities of slime, 

 blood, etc., with which they are from the first associated. The 

 mineral matters of various composition reported remain from the 

 burnt slime, blood, etc. 



Barrcswil (1861) was first to arrive at the correct identification 

 of the lustrous substance as guanin. This compound had been 

 discovered in bird guano by linger in 1845. Barreswil enumerated 

 the properties which led him to that conclusion — its insolubility in 

 water, ammonia, and acetic acid, its behavior on ignition, its solu- 



* Tromsdorff's Journal, Band X, Stiick 2, 1843, p. 3. Paper not seen by the writer and therefore not 

 included in the bibliography. 



