Page:Popular Science Monthly Volume 32.djvu/94

From Wikisource
Jump to: navigation, search
This page has been proofread, but needs to be validated.

results of the two experiments thus computed, may be stated as follows :

In the "floating" of 100 grammes of flesh (body) of the oysters—

 The weight of of— Before dialysis. After dialysis
Water rose from 77∙9 grammes to 96∙6 grammes
Water-free substance fell form 22∙1 " " 20∙6 "
—— ——
 Total flesh 100∙0 " " 117·2 "
Protein was assumed to remain the same 10∙5 " " 10∙5 "
Fat fell from 2∙5 " " 2∙3 "
Carbohydrates, etc., fell from 6∙9 " " 6∙0 "
Mineral salts fell from 2∙2 " " 1∙8 "
—— ——
 Total 22∙1 " 20∙6 "

In brief, according to these computations, the flesh lost between one sixth and one seventh of its mineral salts, one eighth of its carbohydrates, and one twelfth of its fats, but gained enough water to make up this loss and to increase its whole weight by an amount equal to from one seventh to one fifth of the original weight. Assuming the loss of nutritive value to be measured by the carbohydrates and fats which escaped, it would amount to about one tenth of the whole. That is to say, the total nutritive materials were one tenth less after floating than before.

In the liquid portion of the shell-contents, the percentage of water rose and that of the water-free substance fell in a very marked degree. But while the whole percentage of water-free substance was diminished, that of both protein and of carbohydrates rose slightly (the amount of fats was too small to be taken into account), so that the falling off was all in the mineral salts. The experiments do not show the exact increase or decrease in the total amounts of the liquids and their constituents, so that it is impossible to say with entire certainty whether there was or was not an actual gain of protein or fats or carbohydrates. It would seem extremely probable, however, that the liquids received and retained small quantities of these materials from the flesh (bodies) of the animals.

The apparent increase of protein and other materials belonging to the body in the liquids, though slight, is very interesting. I must refer to the detailed account of the experiments for the discussion of it and of the changes in composition of the liquids. The point is that if the changes in composition of the oysters in floating were due to osmose or dialysis alone, we should expect simply a gain of water and loss of salts (and perhaps of soluble carbohydrates). But the flesh seems to have lost a little carbohydrates and fats, and probably protein also, along with the salts, while it was absorbing water, the liquids at the same time gaining more or less of protein and carbohydrates. A way in which this may have come about is suggested by my colleague. Professor Conn, who calls attention to the fact that some mol-