Oysters, as will be observed, contain only a small quantity of fat, and for this reason their total food value is somewhat lower than that of milk. A pint of milk has a value of 325 calories, while the same quantity of oysters has an approximate value of only 250 calories. Because of the difference in the cost of these two foods, oysters costing several times as much as milk, the use of oysters is not so cheap a way of supplying food material.

DIGESTIBILITY OF OYSTERS.--When merely the ability of the digestive tract to handle oysters is taken into consideration, they are said to be easily digested if they are served raw or are properly prepared. This is due to the fact that when taken as a food they are disposed of in a comparatively short time by the stomach. In addition, their absorption from the alimentary tract is quite complete; that is, they contain little or no waste material. But, just as cooking has much to do with the digestibility of other protein foods, so it has with oysters. For this reason, the housewife who wishes to feed her family this food in its most digestible form must thoroughly understand all phases of its cooking.

HEALTHFULNESS OF OYSTERS.--Much illness has been attributed to oysters, and without doubt they have been the cause of some typhoid and some ptomaine poisoning. A knowledge of the reason for these diseases has done much to eliminate them. It is now definitely known that much of the typhoid caused from eating oysters was due to the conditions under which they were grown. In their growth, oysters fasten themselves to stationary things, such as rocks or piles driven into the ground underneath the water, and they obtain their food by simply opening the shell and making use of minute particles of plant and animal life that they are able to extract from the water. When the water was not clean or when sewage was turned into it, typhoid germs were transmitted to persons who took oysters as food. At present, there is scarcely any danger from such causes, for more care is now given to the conditions under which oysters grow. Ptomaine poisoning from oysters was caused by eating them when they had been improperly cared for in storage or had been taken from the shells after they were dead. Unless persons handling oysters know how to take care of them, this danger is still likely to exist.

PURCHASING OYSTERS.--To be able to purchase oysters intelligently, the housewife should be familiar with the names of the various kinds. These names are dependent on the locality from which the oysters come, and include Blue Points, Cape Cods, Cotuits, Lynn Havens, and numerous other varieties. It should be remembered that the varieties raised in different localities are quite distinctive, differing to some extent in both size and appearance. Unless the purchaser is familiar with the different varieties, almost any of the small oysters are likely to be sold to her for one of the small varieties and, likewise, any of the large oysters for one of the large varieties. While this is of small consequence, provided the quality is satisfactory and the price is right, it is well for every housewife to familiarize herself with the names of the various kinds, so that she may know just what variety she is purchasing.

When oysters are bought in the shell, they should be alive, a fact that can be determined by the tightly closed shell, as has already been stated. If the shells are not closed or can be easily pried apart, it may be known that the oysters are not good and that they should be rejected. When it is possible to procure them, oysters that have been removed from the shells immediately after being taken from the beds are preferable to those which have not been removed from the shells before shipping. When purchased out of the shells, oysters should be grayish in color, should have no disagreeable odor, and should contain no excess water or liquid. After being purchased, oysters should be kept on ice unless they can be cooked at once.

The season for oysters is from September to April, inclusive. While in some localities they can be purchased at other times during the year, they are not likely to be so good. In fact, it is not safe to use oysters during the warm months.