SEA-FISHERIES LABORATORY. 



83 



of gills. Variations in the size of the oysters will of 

 course account for small differences, especially with the 

 bodies. 



II 



— Determination of Copper. 





Six Oysters 



French. 

 "Huitres de Marennes" 



Dutch 



American 



Gills only- 

 Bodies minus gills 



Trace 



2*4 mgrnie. 



0-8 

 1-4 



1-7 

 3-3 



" These results show that copper is present normally in 

 both green and in white oysters in small quantity, but 

 that the greenness of the gills of French oysters is certainly 

 not due to this metal — in fact they contain only the merest 

 trace. 



"Experiments by Prof. Herdman on the feeding of 

 oysters with very dilute saline solutions of iron and ol 

 copper salts entirely confirm these analytical data. 

 Beyond a certain amount of post-mortem green staining 

 the oysters did not acquire any green colour."* 



Prof. Thorpe who examined some green oysters obtained 

 by Dr. Bulstrode at Falmouth found that they contained 

 a notable amount of Copper. Possibly, however, the 

 copper, in this exceptional case supposed to be derived 

 from copper mines, may be merely mechanically deposited 

 in the oyster, and although present may not be the actual 

 cause of the colour, as we found the living oyster would 

 not become coloured from copper salts. 



Since our report on oysters and disease was read before 

 the British Association in September, a bulky Local 

 Government Board Keport Supplement by Dr. Thorne 



* See, for further details our account of these experiments in last 3'ear's 

 Report, p. 62. 



