OYSTERS. The most common oyster in our market is the Ostrea Virginiana, found in all the beds of the Eastern States, perhaps the choicest of which are those from Chesapeake Bay, where they are cultivated very extensively. The total oyster trade, from Maine to California, has been valued at $50,000,000 annually. They are out of season from May to September, when they are spawning, and are consequently thin and unhealthy.
"A valuable peculiarity of the animal," says one writer, "is the possibility of sustaining life for a long time after being removed from its native element; properly cared for, they may be kept alive and in good condition for weeks ; if they are placed in a cool, damp place, with the mouths up, and occasionally sprinkled with brackish water, they are said not only to keep alive but to fatten, this tenacity of life is owing to the liquor contained within the shells, which serves to sustain the respiratory currents ; but when the liquor, through evaporation or other causes, departs, the oyster at once dies. When removed from the shell, by proper care, the eysters may be kept in an edible condition for several days ; in this case it is necessary to exclude it from the accom panying liquor, for although this is the medium by which exist ence is sustained whilst in the shell, yet it has been found to have the opposite effect when it is removed from the shell; there fore, if it is desired to transport them to any distance, or other wise dispose of them by which time is consumed before they are utilized, they are removed from their liquor and carefully washed, frequently as often as five or six times, until no particle of any substance but the oyster itself remains ; thus prepared and kept cold and excluded from the air, they may be kept eight to ten days without injuring their flavor, or otherwise affecting their con dition as an article of food." Dr. William Roberts, in an interesting series of lectures on digestive ferments, published in the Lancet, says, regarding raw oysters: The practice of cooking is not equally necessary in re gard to all articles of food. There are important differences in
this respect, and it is interesting to note how correctly the experi ence of mankind has guided them in this matter. The articles of food which we still use in the uncooked state are comparatively few, and it is not difficult in each case to indicate the reason of the exemption. Fruits, which we consume largely in the raw state, owe their dietetic value chiefly to the sugar which they contain; but sugar is not altered by cooking. Milk is consumed by us, both cooked and uncooked, indifferently, and experiment justifies this indifference, for I have found, on trial, that the di gestion of milk by pancreatic extract was not appreciably hastened by previously boiling the milk. Our practice in regard to the oyster is quite exceptional, and furnishes a striking example of the general correctness of popular judgment on dietetic ques tions. The oyster is almost the only animal substance which we eat habitually, and by preference, in the raw or uncooked state, and it is interesting to know there is a sound physiological reason at the bottom of this preference. The fawn-colored mass which constitutes the dainty part of the oyster is its liver, and this is little else than a heap of glycogen. Associated with the glycogen. but withheld from actual contact with it during life, is its appro priate digestive ferment—the hepatic diastase. The mere crush ing of the dainty between the teeth brings these two bodies to gether, and the glycogen is at once digested, without other help, by its own diastase. The oyster in the uncooked state, or merely warmed, is, in fact, self-digestive. But the advantage of this provision is wholly lost by co ,king, for the beat employed imme diately destroys the associated ferment, and a cooked oyster has to be digested, like any other food, by the eater's own digestive powers.