24 



OYSTERS AND DISEASE. 

 Total Iron present in Oysters. 



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

 must be borne in mind. 



From these figures in the above tables it is evident that there is not an 

 excessive quantity of iron in the gills of the green oysters — the proportion of iron in 

 the gills as compared with the rest of the body is somewhat more (1:2) than that 

 found in Dutch oysters (1 : 3.7), but much less than in American oysters, which are 

 white (1.4 : 1). The comparison is purposely made on the absolute quantity of metal 

 in the gills and the rest of the body, as any other basis for calculation is fallacious. 



Chatin and Muntz reckon on the weight of the dried organic matter present 

 but it was not found possible to get anything approaching constant weights in this way. 

 This may to some extent account for the difference in our results, but we should also 

 like to point out that although the ratio of iron in the gills and the rest of the body in 

 green and in brown oysters is from 1 : 1.8 (feebly green) up to 1 : 2.3 (very green), they 

 also instance white oysters with a proportion of 1 : 1.6. 



It is certainly somewhat strange that they find more iron in the gills than in the 

 rest of the body in all cases, which is not the case in our own experiments. But the 

 quantities of metal present are so small that, since they do not state how many oysters 

 were taken for analysis, and employ the permanganate method for the estimation of the 

 iron, it is difficult to say what degree of absolute accuracy their results represent, and 

 therefore to judge in how far their analytical data justify their conclusions. 



From two points of view the above results show that the greenness of the gills 

 of French oysters is certainly not due to iron : — 



(1) Because the gills of the green oyster contain less iron than the rest of the body. 



(2) Because the proportion of iron in the gills as compared with the .rest of the 



body in white (American) oysters is greater than in the green. 

 That our method is reliable is shown by two determinations of the iron in the 

 gills of American oysters, one giving 2.3 and the other 1.8 mgrme. of iron per six sets 

 of gills. Variations in the size of the oysters will of course account for small differences, 

 especially with the bodies. 



