On a Green Leucocytosis in Oysters. 



33 



The Green Leucocytosis. 



We first noticed this diseased condition in the autumn of 1895, in 

 some ordinary American oysters (" bine points "), belonging to the 

 species Ostrea virginica, which had been imported into Liverpool aud 

 relaid near Fleetwood, in the estuary of the Wyre. Since then many 

 hundreds (probably several thousands) of American oysters have 

 been examined by us, and we have seen all degrees of the leuco- 

 cytosis. It manifests itself in patches and streaks of green on the 

 mantle and other parts of the integument, in engorgements of the 

 blood vessels, especially of those that ramify over the surface of 

 the viscera, and in masses of green-coloured leucocytes in the heart. 

 This green condition, although much less frequently seen in " natives " 

 (0. edulis), is occasionally met with there also, and we have recently 

 had some specimens from Falmouth with very well-marked green 

 hearts, due to an accumulation of leucocytes laden with green 

 granules in the ventricle. Such hearts are of frequent occurrence 

 in the diseased American oysters ; after death the mass of leucocytes 

 subsides to the bottom of the cavity, leaving the clear plasma above. 

 It is thus easy to demonstrate that the colour is due to the leuco- 

 cytes, and to the leucocytes alone. 



The blood of these oysters contains a great variety of more or less 

 colourless and more or less green and granular corpuscles, all of 

 which may be termed leucocytes. They are apparently all amoeboid 

 wandering cells, comparable to the colourless corpuscles of the blood 

 of higher animals. The larger and (probably) older of the leuco- 

 cytes are very coarsely granular and very opaquely green. It is 

 these that give the colour in bulk. We find them in masses in the 

 heart, in both auricle and ventricle, in the vessels, where they are 

 sometimes so abundant as to engorge or inject certain parts of the 

 system, in the lacunar spaces of the connective tissue of the mantle 

 and other organs, and also in the more solid parts of the tissues 

 wandering amongst the other cells, wedged into the epithelium and 

 coming out in great numbers on the surface of the body. Some of 

 these latter, when found in the ectoderm and on the surface, are 

 very markedly eosinophilous ; those in the vessels are not so markedly 

 so. When stained with osmic acid the granules of the leucocytes 

 become black. After treatment with fat solvents, however, some of 

 the leucocytes are still very granular. 



In sections which have not been stained, the granules of the 

 leucocytes have a distinctly brown colour, recalling the appearance 

 of the granules in the liver cells in unstained sections in cases of 

 pernicious anemia. 



We opened many batches of American oysters, 100 at a time, and 

 in all cases where the green tint was present in the mantle, heart, or 



VOL. lxii. D 



