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XLIT.—Some Observations on Fish, in relation to Diet. By Joun Davy, M.D., 
F.R.S. Lond. & Edin., Inspector-General of Army Hospitals, &c. 
(Read 18th April 1853.) 
What are the nutritive qualities of fish, compared with other kinds of animal 
food? Do different species of fish differ materially in degree in nutritive power ? 
Have fish, as food, any peculiar or special properties? These are questions, 
amongst many others, which may be asked, but which, in the present state of 
our knowledge, I apprehend it would be difficult to answer in a manner at all 
satisfactory. 
On the present occasion, I shall attempt little more than an opening of the 
inquiry, and that directed to a few Renin: those alluded to in the fore- 
going queries. 
1. Of the Nutritive Power of Fish. 
The proposition probably will be admitted, that the nutritive power of all the 
ordinary articles of animal food, at least of those composed principally of mus- 
cular fibre, or of muscle and fat, to whatever class belonging, is approximately 
denoted by their several specific gravities, and by the amount of solid matter 
which each contains, as determined by thorough drying, or the expulsion of the 
aqueous part, at a temperature such as that of boiling water, not sufficiently high 
to effect any well-marked chemical change. 
In the trials I have made, founded on this proposition, the specific gravity has 
been ascertained in the ordinary hydrostatical way ;—the portions subjected to 
trial, in the instance of fish, have been taken from the thicker part of the back, 
freed from skin and bone, composed chiefly of muscle. And the same or similar 
portions have been used for the purpose of determining their solid contents, dried 
. in platina or glass capsules of known weight, and exposed to the process of drying 
till they ceased to diminish in weight. 
The trials on the other articles of diet, made for the sake of comparison, both 
as regards specific gravity (excepting the liquids), and the abstraction of the 
hygroscopic water, or water capable of being dissipated by the degree of tem- 
perature mentioned, have been conducted in a similar manner. 
The balance used was one of great delicacy, at home, or a small portable one, 
when from home, of less delicacy, yet turning readily with one-tenth of a grain. 
The results obtained are given in the following tables. In the first. on some 
different species of fish; in the second, on some other articles of animal food. 
I have thought it right, whenever it was in my power, to notice not only the 
time when the fish were taken, but also the place where they were procured,—not 
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