MICRO-CHEMISTRY OF THE GREEN OYSTERS. 3 1 



potassic ferrocyanide, after previous immersion in very dilute acid, a distinct reddish 

 colouration is obtained, visible to the naked eye. Fig. 3 on PI. VII. shows part of such a 

 preparation under the microscope. Colourless corpuscles obtained from oysters which are 

 not green do not give these reactions. The best preparations of the copper-containing 

 leucocytes are obtained by treating freshly-teased vessels, or sections of vessels, after 

 imbedding in paraffin, with the various reagents {see PI. VII., Figs, i, and 4 — 9). The 

 leucocytes in bulk then give well-marked reactions ; in many of the cells the reactions can 

 be plainly seen, the granules in them assuming a reddish tint in the case of potassic 

 ferrocyanide, or violet with haematoxylin. 



Vessels and Heart. — In well-marked cases of leucocytosis the green heart (PI. 

 VII., Fig. 2, b) may be removed from the oyster, treated first with dilute acid, and then 

 with potassic ferrocyanide, when a brown colouration is readily obtained ; the organ 

 may then be dehydrated, passed through oil of cloves, and mounted in Canada balsam. 

 Similarly the vessels may be stripped off from the mantle and treated as above — such 

 specimens are seen in Figs, i and 4. The most instructive preparations are, however, 

 obtained by first hardening the green oysters. Figs. 5 — 9 on PI. VII., and Figs. 5 and 

 6 on PI, VIII., show a series of sections through the body of the oyster, and passing 

 through one of the larger pallial sinuses close to the mantle edge, which in this case 

 was engorged with green leucocytes. One section, Fig. 7, has been treated with potassic 

 ferrocyanide ; Fig. 9 has been stained with the colourless solution of hsematoxylin ; 

 Fig. 8 has been treated with ammonium hydrogen sulphide ; and Fig. 6 is an untreated 

 section which plainly shows the green colour. Similar reactions are demonstrated in 

 our series of sections (which it seems unnecessary to reproduce, as they show the same 

 colours as Figs. 6 — 9) passing through the auricles and ventricle ; the conjoined auricles, 

 it will be observed, have normally a dark brown colouration, and do not give any 

 change, the ventricle containing the leucocytes only reacting. 



Under high magnification {see PI. VIII.) the best pictures* are yielded by the 

 haematoxylin-treated sections. Wherever there are copper-containing leucocytes, these 

 stain immediately with the reagent, and by their colour stand out in marked contrast 

 with the surrounding colourless tissue. This is well illustrated in PI. VIII., Figs, i to 

 4. In many of the sections we found that the large eosinophilous cells in the mantle 

 of the green oysters gave a strong reaction with haematoxylin ; this was the case in 

 the oyster from which PI. V., Fig. 8, was made. That eosinophilous cells should give 

 such a reaction is remarkable, and is to be explained by the fact that in some cases 

 these cells contain copper, 



* In these and the other figures illustrating the micro-chemical reactions, we have given the colour effects, 

 distribution of granules, and shades, but have not represented the further histological details which these methods were 

 not intended to demonstrate. 



