566 



REPORT — 1898. 



Finally, the total iron in a variety of oysters -w^as determined in order 

 to ascertain the normal quantity present. These data, which are tabulated 

 below, show a fairly constant proportion of iron per oyster, from 0-15 to 

 0'36 mgrme., or from 0'18 to 0-65 per cent, on the ash. 



In considering the variations in quantity, the very small amounts of 

 metal present must be borne in mind. 



It may be added that although Carazzi has attributed the green colour 

 of French oysters to iron taken up from the mud of the oyster-park or 

 ' claire,' experiments on feeding oysters with very dilute solutions of iron 

 salts (0-02 to 0-01 per cent.) carried on in conjunction with Professor 

 Herdman produced no green colouration whatever. The only result was 

 a certain amount of ' browning ' throughout the oyster, the gills being no 

 more affected than the rest of the body. More recently Carazzi has sliown 

 that oysters fed with similar dilute iron solutions acquire a pale yello-jvish 

 colour in certain parts (branchial epithelium and the oesophageal mucous 

 membrane], and that in these parts microscopic tests show the presence of 

 granules of iron. The actual meaning of these results can hardly be recog- 

 nised without quantitative data. 



The Presence of Copioer in Oysters. — Fredericq has shown that a certain 

 small amount of copper is present normally in the hsemocyanin of the 

 blood of crustaceans and molluscs. The quantity thus present in oysters 

 of different origin is fairly constant as shown in the following table : it 

 varies from 0-25 to 0-66 mgrme. per oyster, or from 0-30 to 1"18 per cent, 

 on the ash. 



0-4 mgrme. per oyster may be taken as an average, a quantity slightly 

 greater than the average iron (0-26 mgrme.). The calculated percentages 

 on the ash show greater variations, due to tlie very considerable differences 

 in the total quantities of mineral salts present, and it is probably to this 

 last factor that the popularly recorded differences in taste of the various 

 kinds of oysters is really due. Certainly the minute quantities of copper 

 and iron present cannot account for them. 



