OYSTERS 129 



or waterways), and they rid themselves of any possible 

 infection. It is the interest of the oyster merchant to 

 make sure that this treatment is strictly enforced. It is 

 a noteworthy fact that the anciently established habit of 

 drenching an oyster with vinegar before eating it is 

 precisely the best treatment, except cooking them, which 

 could have been adopted in order to destroy the vitality 

 of typhoid germs although the existence of such germs 

 was unknown when the practice arose, and vinegar or 

 lemon-juice was taken with uncooked oysters as a matter 

 of taste, not as a safeguard. 



The oyster is sometimes grandiloquently styled " the 

 succulent mollusc " and it is classed together with other 

 bivalve shells and true " shell-bearing " shell-fish, such as 

 whelks and snails (not lobsters and crabs, which are 

 Crustacea), in a great division of animals known to 

 naturalists as the Mollusca. This word is only a Latin 

 form of the name Malakia, which was given to the 

 cuttle-fishes by that wonderful man Aristotle, the Greek 

 and means " soft creatures." A bivalve, or two-shelled 

 mollusc, like the oyster, may be compared to an oblong 

 notebook. The hard covers correspond to the two 

 shells and the back to a horny piece by which the two 

 shells are united, forming the hinge. If you place a 

 piece of indiarubber (a thickish bit) between the covers 

 of the notebook so that it lies near the back, and then 

 try to shut the book, you find that it requires some 

 pressure to do so ; when you leave off pressing them the 

 covers gape. The horny hinge-piece or ligament of the 

 shells of the oyster and other bivalves acts in this way. 

 The shells are only kept closed by a strong muscle, 

 which runs across from shell to shell (Figs. 28 and 30772). 

 When the oyster is at rest or when it is dead the muscle 

 does not act, and the elastic hinge-piece or ligament 

 causes the shells to gape. The animal within the shells 

 9 



