IRON AND COPPER IN OYSTERS. 
27 
down copper from old mines, and the mud of which was found by Thorpe to contain 
0.148 per cent, of copper. Normal sea-water contains such an excessively small quantity 
of copper that it was not found possible by Dr. Kohn to detect its presence, even 
electrolytically, in a litre of sea-water, after concentration. 
Taking, finally, the green leucocytosis found in some American oysters, the six 
greenest and six whitest of 120 of these oysters, as re-laid on our coast, were chosen 
for analysis ; also a quantity of the greenest portions of the greenest oysters was 
selected from another batch, and compared with the corresponding portions of the 
whitest oysters. The iron was not determined in the latter comparison, owing to the 
possible contamination by that metal in the cutting. 
The following were the results obtained : — 
Oysters. 
Copper. 
Iron. 
Ash. 
Mgrnie. 
Copper 
per 
Oyster. 
Mgrme. 
Iron per 
Oyster. 
Per cent. 
Copper 
on Ash. 
Per cent. 
Iron 
on Ash. 
Green 
0.0158 
0.0091 
1. 1450 
2.63 
1.52 
r.38 
0.79 
White 
0.0042 
0.0036 
1.094 8 
0.70 
0.60 
0.38 
0.33 
Greenest parts 
0.0033 
0.0780 
4-23 
Whitest parts 
0.0009 
0.0452 
1.99 
The excessive quantity of copper in the selected green oysters is 3.75 times that 
in the white ones, calculated per oyster, and 3.63 times calculated on the ash. In the 
selected parts the total copper present calculated on the ash is high in both cases, and 
the green parts again show a marked excess in the proportion of 2.1 to i. The copper 
and iron in the white specimens are about normal, but the increased quantity of iron 
in the green is marked, being 2.5 times that of the former. Still there is relatively a 
large excess of copper as compared with iron in the green oysters, as is evident from 
the analyses, the ratio being i.i : i for the white, and 1.8 : i for the green. 
It is to be concluded, therefore, that the green colour of these diseased American 
oysters is coincident with the distribution of the excessive quantity of copper present, 
and that the copper is in consequence to be regarded as the cause of the colour. The 
histo-chemical investigations given further on confirm this conclusion. 
Manganese was also found by Dr. Kohn to be present in several of the kinds 
of oysters analyzed. Its detection is readily effected in the electrolytic method of 
analysis, as it separates at the anode as peroxide. Colne oysters contain 0.14 mgrme. 
per oyster, a quantity rather smaller than the amount of iron present. 
We must now turn to Dr. D. Carazzi's recent papers, in which he tries to show 
that the green colouration in oysters is in all cases a healthy condition, caused by the 
absorption of iron as a nutrient material from the surrounding mediiun by means of the 
surface epithelial cells, such as those of the branchiae and palps. A good deal that is 
