SIXTEENTH ANNUAL MEETING. 



37 



THE CHEMICAL CHANGES PRODUCED IN OYSTERS 

 IN FLOATING, AND THEIR EFFECT UPON 

 THE NUTRITIVE VALUE. 



BV PROE. W. O. ATWATER. 



It is a common practice of oyster dealers, instead of selling 

 the oysters in the condition in which they are taken from the 

 beds in salt water, to first place them for a time, forty-eight 

 hours, more or less, in fresh or brackish water, in order, as the 

 oyster-men say, to "fatten" them, tlie operation being called 

 "floating" or "laying out." By this process the body of the 

 oyster acquires such a plumpness and rotundit}-, and its bulk 

 and weight are so increased as to materially increase its selling 

 value. 



The belief is common amoii^ oyster-men, tliat this " fattening " 

 is due to an actual gain of flesh and fat, and that the nutritive 

 value of the oyster is increased. 



A moment's consideration of the chemistry and physiology of 

 the svibject will make it clear, not only that such an increase of 

 tissue-substance in so short a time and with such scanty food- 

 supply is out of the question, but that the increase of volume 

 and weight of the bodies of the oysters is just what would be 

 expected from the osmose or dialysis which would naturally take 

 place between the contents of the bodies of the oysters as taken 

 from salt water, and the fresli or brackish water in which they 

 are floated. 



If we fill a bladder with salt water and then put it into fresh 

 water tlie salt water will gradually work its way out through 

 the [)()res of the bladder and, at the same time, the fresher water 

 will enter the bladder; and further, the fresh water will go in 

 much more rapidly than the salt water goes (iut. The result 

 will be that the amount of water in the bladder will be increased_ 

 It will swell by taking up more water than it loses, while, at the 

 same time, it loses a portion of the salt. 



It docs this in (obedience to a physical law, to which the term 

 osmose and dialysis are applied. In accordance with this law, 



