28 
OYSTERS AND DISEASE. 
Stated by Carazzi is quite correct, but these are points which were known before. 
The novel statements are, we believe, entirely erroneous, and are the results either of 
mistaken observations, or inferences from observations. 
He rightly states that the Marennes green oysters may retain their colour for 
weeks or even months when taken to other waters in which greening does not take 
place. It is true of our green Marennes oysters, kept for weeks practically without food 
in tanks in the laboratory. This fact is well known, and has been mentioned by various 
writers from Bouchon-Brandely, in 1871, onwards; but does it not tell strongly against 
Carazzi's own view that the green substance is a nutrient material on its way from the 
surface epithelium to the liver ? Is it at all likely that, if the green " Marennin " is a 
nutrient material in process of metabolism, it will remain for months in the superficial 
tissue (which by Carazzi's hypothesis has just absorbed it) after the source of supply 
has been removed ? That is very improbable, even admitting Carazzi's statement as to 
the distribution of the iron-containing Marennin in the superficial cells to be correct ; 
but we do not admit it. As we have shown above, we have abundant evidence that 
the green granules are constantly in the " macroblasts," and comparatively rarely in the 
ciliated epithelium. In fact, in all essential points of structure — the details of which 
need not be gone over again — we agree with Lankcster, Pclseneer, J. Chatin, and 
De Bruj^ne, and differ from Carazzi in his criticism of these former authors. 
Moreover, all the observations made by ourselves, and those recorded by others, 
on the West Coast of France are in accord with the view that the " greening " depends 
upon microscopic food-organisms in the sea-water. Bornet and Ad. Chatin showed, in 
1894, that the greening comes on suddenly in parks at Sables d'Olonne, where it was 
not present before. The greening, again, only takes place at a certain time of year, 
usually autumn, which agrees with the periodic distribution of minute organisms. 
Bouchon-Brandely says that at Marennes it is a common observation that the oysters 
only become green when the water in the " claires " (ponds) has become green with 
microscopic plants. It is known at La Trembladc that when a claire is in the greening 
condition it must not be emptied, as a change of the water might deprive it of its 
greening properties. Moreover, the greening must be due to tlie contents of the water, 
since in the Island of Cuhan (La Trinite River) Dr. Gressy has successfully reared 
green oysters in basins excavated in the solid rock. 
We must call attention to the way in which Carazzi has peremptorily denied * 
or misrepresented the results of some of the many investigators of molluscan anatomy 
and physiology with wliom he does not agree. For example, he says of Ryder's 
statement that the ventricular part of the heart may be green, " he is certainly mistaken," 
&c. We are able, however, to state that Ryder was perfectly correct, and that it is 
* It is perhaps sufficient, as an example of Carazzi's style, to state that after alkiding to the work of Lankester, 
Pelseneer, and others, he makes the sweeping assertion :— "Tulto quel ch' e stato detto finora suUe ostriche verdi 
e completamente sbagliato, ed e la conseguenza di osservazioni o infondaie o malamente interpretate." 
