OXYGEN CONSUMPTION OF OYSTERS 
503 
The problem was complicated by the fact that the early investigators did not 
clearly distinguish between the types of green pigmentation and confused the blue- 
green pigmented oysters with the green-gilled ones. It is generally agreed at the 
present time that the former is associated with an increase in copper content and 
that the latter, which may have a normal copper content, is due to the accumulation 
of the pigment of the diatom Navicula ostearia. 
Hunter and Harrison (1928) have shown that oysters taken from the vicinity of 
manufacturing centers may contain appreciable quantities of arsenic, zinc, and lead, 
besides copper. In some samples taken from New York Harbor and from Con- 
necticut waters, the metallic contamination could be easily traced to the pollution 
of water by trade wastes. Yet in several instances oysters from areas located far 
from any known source of metallic contamination were found to contain considerable 
quantities of zinc and copper. The question of the source of copper in the sea and 
of the mechanism of its accumulation by the oyster has not yet been satisfactorily 
solved. Hunter and Harrison (loc. cit.) believe that oysters will absorb from the 
water almost any substance which it contains. The problem, however, requires 
further investigation. 
A review of the literature reveals the fact that no systematic efforts were made to 
determine the chemical nature of the green pigment of oysters. Such an effort was 
made during the summer of 1927 by the senior author and Dr. Samuel Lepkofsky. 
First a series of analyses for copper was made on a large number of green oysters from 
Long Island Sound and of normal oysters from Wellfleet Harbor, Mass. The latter 
locality was selected because it was known that green oysters never occurred in Well- 
fleet Harbor. For microchemical reactions, sections of green and normal oysters 
preserved in absolute eth 3 7 l alcohol and embedded in paraffin were treated with po- 
tassium ferrocyanide and with haematoxylin. The results of these analyses con- 
firmed fully the conclusions of Herdman and Boyce that the intensity in green color 
was in proportion to the copper content in the oyster and that histologically the copper 
is located in the green leucocytes. 
The next step was to isolate the green substance and to attempt to determine its 
chemical composition. Unfortunately, because of the separation of Doctor Lep- 
kofsky from the bureau, this work has not been finished. It is, however, desirable to 
give a brief account of the results so far obtained. 
The green pigment generally associated with mollusks is a copper-protein com- 
plex, hemocyanin. It was thought that the green compound in oysters might be of 
a similar nature. The isolation of the green substance was attempted with the view 
of studying its chemical properties and using this information in an effort to remove 
the substance from the oyster or prevent its appearance. To obtain the pigment, 
oysters were ground in water with pure sand, which had been previously treated with 
strong HC1 and carefully washed. 
Green extracts obtained by this method were then- saturated with (NH 4 ) 2 S0 4 
which caused all the proteins to be precipitated, but the pigment was not thrown out 
of solution. This indicated it was not a hemocyanin or a copper proteinate of any 
kind. Treatment with Na 2 S0 4 at 37° C. did not precipitate the green color. 
Finally, dialysis showed the pigment passed through collodion sacs which held 
back congo red. This indicated that the green compound was of a small molecular 
size. 
