!\riCRO-CHEMISTRY OF THE GREEN OYSTERS. 3 1 
potasbic ferrocyanide, after previous immersion in very dilute acid, a distinct reddisii 
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 ha^matoxylin. 
Vessels and Heart. — In well-marked cases of leucocytosis the green heart (PI. 
VII., Fig. 2, d) 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 haematoxylin ; 
Fig. 8 has been treated with ammonium hydrogen sulphide ; and P^ig. 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 rejoroduce, 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, anrl 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 
hii^matoxylin-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 hitmatoxylin ; this was the case in 
the oyster from which PI. V., P'ig. 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, \vc have given the colour eflects, 
distribution of granules, and shades, but have not represented the further histological details which these methods were 
not intended to demonstrate. 
