SEA-FISHERIES LABORATORY. 



Determination of Copper. 



143 



Six Oysters. 



French 

 ' Huitres de Marennes. ' 



Dutch. 



American. 



Gills only 



Bodies minus gills... 



Trace 



1*4 mgrme. 



0-8 

 1-4 . 



1-7 

 3-3 



' These data show conclusively that the green colour of 

 the gills of French Oysters is also in no way connected 

 with the copper present. 



' Quantities of copper greater than those recorded point 

 to abnormal conditions. Such have been found to occur 

 with certain Falmouth Oysters, and in an especially 

 interesting manner with the green leucocytosis of American 

 and Falmouth Oysters — the diseased condition referred to 

 above. 



' Falmouth Oysters. — The presence of relatively large 

 quantities of copper in Falmouth and other Cornish 

 Oysters has been repeatedly associated with their bluish- 

 green colour. Dr. T. E. Thorpe* states that these 

 Oysters, the colour of which, both in character and dis- 

 tribution, is quite different from that of the Marennes 

 Oysters, contain on the average about 1'3 mgrme. of 

 copper per Oyster. This large proportion is, Dr. Thorpe 

 says, " obviously caused by the mechanical retention of 

 cupriferous particles." On relaying they lose their 

 colour, and the quantity of copper present becomes 

 normal, 0*4 mgrme. per Oyster. 



' Six Falmouth Oysters, the bodies of two of which were 

 of a distinct arsenic-green colour, were dried at 100° C, 

 and then digested with water and subsequently with dilute 

 hydrochloric acid. The extract contained about half the 

 total copper present, showing that the metal is partially, 



*." Nature," 1896, p. 107. 



