Open main menu

Page:Popular Science Monthly Volume 32.djvu/96

This page has been proofread, but needs to be validated.

ter, if the above explanation is correct, are caused partly by osmose, and partly by special secretive action, the cell-walls and outer coat of the body of the oyster corresponding to the walls of the alimentary canal in the human body. The forms of vital activity in the two cases are different, but osmose is concerned in both.

The main points here urged may be very briefly summarized:

1. In the floating of oysters for the market, a practice which is very general, and is also used for other shell-fish, the animals are either taken direct from the beds in salt water, and kept for a time in fresher (brackish) water before they are opened, or water is added to the shell-contents after they are taken out of the shell. When thus treated, the body of the animal takes up water and at the same time parts with some of its salts, while small quantities of the nutritive ingredients also escape. The oysters thus become more plump, and increase considerably in bulk and weight, but the quantity of nutritive material, so far from increasing, suffers a slight loss.

2. In the experiments here reported, the increase in bulk and weight was from one eighth to one fifth of the original amounts. This is about the same as is said to occur in the ordinary practice of floating or "fattening" for the market. According to this, five quarts of oysters in their natural condition would take up water enough in "floating" to increase their bulk to nearly or quite six quarts, but the six quarts of floated oysters would contain about one tenth less of actual nutrients than the five quarts not floated.

3. The gain of water and loss of salts are evidently due to osmose. The more concentrated solution of salts in the body of the animal, as taken from salt water, passes into the more dilute solution (fresher water) in which it is immersed, while a larger amount of the fresher water at the same time enters the body. But part of the exchange, and especially that by which other materials, carbohydrates, protein, etc., are given off in small quantities, is more probably due to a special secretory action.

4. The flavor of oysters is often much improved by the removal of the salts in floating, and they are said to bear transporting and to keep better. When, therefore, the oyster-man takes "good fat oysters" which "yield five quarts of solid meat to the bushel" and floats them so that "they will yield six quarts to the bushel," and thus has an extra quart, and that a quart of the largest and highest-priced oysters, to sell, he offers his customers no more nutritive material—indeed, a trifle less—in the six quarts than he would have done in the five quarts if he had not floated them. But many people prefer the taste of the floated oysters, and since they buy them more for the flavor than for the nutriment (at ordinary prices, the nutrients in oysters cost the buyer from three to five times as much as similar nutrients in the better kinds of meat), doubtless very few customers would complain if they understood all the facts. And considering that the practice is