Mr. A. W. E. O'Shaughnessy on Green Oysters. 223 



cases on record in which fatal consequences have followed their 

 use as an article of food, there is reason to suspect that copper 

 has been the chief cause of the evil. 



So far back as the year 1713, mention is made of a certain 

 luxurious supper given by an ambassador at the Hague, who, 

 in order that no delicacies might be wanting, procured green 

 oysters from England. All who eat of them are said to have 

 been immediately seized with severe colics, and to have been 

 cured with great difficulty. Lentilius, on whose authority this 

 account rests, states that it was afterwards ascertained that the 

 merchant, whom he anathematizes with his whole race, had 

 palmed upon the ambassador some common oysters tinted with 

 copper, for the true greens*. 



Another case is recorded by Dr. Chisholm in the * Edinburgh 

 Medical and Surgical Journal,' vol. iv. p. 400. He was informed 

 by Mr. William Newton, of St. Croix, that some time after the 

 British frigate 'Santa Monica' was cast away on the coast of the 

 island of St. John (one of the Virgin Islands), oysters grew on 

 her bottom, which was coppered. Many people ate of these 

 oysters; and although the consequence was in no case fatal, it 

 was dangerous and unpleasant in a very great degree, producing 

 cholera and excruciating tormina. 



With regard to those oysters in which the green tint is not 

 due to any such deleterious cause, but, on the contrary, rather 

 enhances their value as a delicacy, many very different explana- 

 tions have been offered of the manner in which that colour is 

 acquired. It has been said that the water in the artificial beds, 

 remaining stagnant in warm weather, becomes green, and soon 

 communicates the same colour to the oysters themselves ; and 

 Dr. Johnston, speaking of the French oysters, says that, in order 

 to communicate to them a green colour, which, as with us, en- 

 hances their value in the market and in the estimation of the 

 epicure, they are placed for a time in tanks or "parks," formed 

 in particular places near high-water mark, and into which the 

 sea can be admitted at pleasure by means of sluices ; the water 

 being kept shallow and left at rest is favourable to the growth 

 of the green Confervse and Ulvse; and with these there are 

 generated at the same time innumerable minute crustaceous 

 animalcules which serve the oysters for food, and tincture their 

 flesh with the desirable hue. 



In 1820 M. Benjamin Gaillon made a series of observations 

 upon this subject, which he communicated to the Academic des 

 Sciences de Rouen, and which led him to the conclusion that 

 the green colour of oysters is due to the absorption of micro- 

 scopic animalcules allied to the Vibrio tripunctatus of MUller, 

 * Dr. Johnston's ' Introduction to Conchology,' p. 19. 



