86 THE POPULAR SCIENCE MONTHLY. 



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 in- 

 gredients also escape. The oysters thus become more plump, and in- 

 crease 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 tins, 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 tbe 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 spe- 

 cial 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 

 80 that " they will yield six quarts to the bushel," and thus has an ex- 

 tra 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 bet- 

 ter kinds of meat), doubtless very few customers would complain if 

 they understood all the facts. And considering that the practice is 



