57 



and produce diseases of serious gravity sometimes epi- 

 demic in character. The more dangerous of the ailments 

 which afflict oysters under cultivation at Arcachon are 

 those known locally as doussain or doufain, typhus, 

 chambrage, boudeuse or rachitique and disease of the 

 adductor muscle. 



Under the name of doucain, Arcachon parkers refer 

 to the chief ailment caused by an excessive reduction in 

 the salinity of the water bathing the oyster beds, conse- 

 quent upon Moods resulting from prolonged rains over 

 the catchment areas of the streams emptying into the 

 Arcachon basin, whence doucain, the disease caused by 

 can douce. Among marine animals the oyster is one of 

 the most tolerant towards variations of salinity, so long 

 as they are not excessive and long continued. If they 

 be, the oysters gradually sicken and if the adverse 

 conditions be further continued widespread death ensues. 

 The first sign of a reduced salinity is seen in the 

 gradual enlargement and " plumping " of the body, the 

 liver suffering great enlargement (hepatitis). This con- 

 dition of hypertrophy of the tissues in general and of 

 the liver and other glandular organs in particular is due 

 to the same cause and is indeed identical with the 

 artificial and rapid " fattening " to which ignorant or 

 unscrupulous dealers often subject consignments of 

 oysters to be consumed forthwith, a process consisting 

 of laying the oysters in ponds or in tubs containing 

 fresh water. The "fattening" in merely the osmotic 

 exudation of dense fluid from the cells and vessels of 

 the body and replacement by the in-taking of a larger 

 volume of the less dense fluid without. More water 

 enters than leaves the tissues in obedience to a well- 

 known physical law, with the result that distension and 

 discomfort first ensue, followed by a disorganization of 

 secretory functions and the eventual break-down and 

 death of the entire organism. Parks situated towards 

 the eastern and northern (interior) extremities of the 

 basin are most liable to surfer from this disease, beino- 



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