----‘Each creek and bay,
With fry innumerable swarm and shoals
Of fish, that with their fins and shining scales,
Glide under the green waves; * * *
* * * part single, or with mate
Graze the sea-weed, their pasture, and through groves
Of coral stray; or sporting, with quick glance,
Show to the sun their way’d coats dropp’d with gold.’
The modes of preserving fish are various; they are salted and dried,
smoked and potted, baked or marinated, preserved in oil, and pounded in
a dry mass.
Several savage nations possess the art of preparing fish in a great
variety of ways, even as a kind of flour, bread, &c.
Dr. Davy, commenting upon the remarkable facts respecting the exemption
of fish-eating persons from certain diseases, suggests that there is
undoubtedly something in the composition of fish which is not common to
other articles of food, whether vegetable or animal. He believes this
consists of iodine. He says, that in all instances in which he sought
for this substance in _sea fish_ he has found it; and also traces of it
in migratory fish, but not in _fresh-water fish_.
The trials he made were limited to red gurnard, mackerel, haddock,
common cod, whiting, sole, ling, herring, pilchard, salmon, sea-trout,
smelt, and trout.
The experiment was as follows.--He dried and charred, lixiviated,
reduced to ashes, and again washed from a quarter of a pound to a pound
of fish.
A good deal of limy matter was afforded from the washings of the
charcoal of the sea fish.
The saline matter was principally common salt, had a pretty strong
alkaline reaction, and by the blue hue produced by starch and _aqua
regia_, afforded a clear proof of the presence of iodine. Only a slight
trace was detected in the fresh-water salmon, sea-trout, and smelt. In
the spent salmon descending to the sea, only just a perceptible trace
was observable, and no trace in either parr or trout.
Dr. Davy states further, that he has detected it in an unmistakable
manner in the common shrimp; also in the cockle, mussel, oyster, crab,
&c.; nor is this remarkable, considering that it enters into the
greater part of the food of fishes.
He observes, also, that cod liver oil is well established as an
alterative or cure of pulmonary consumption, and as this oil contains
iodine, the inference is, that sea fish, generally, may be alike
beneficial. The practical application of this inquiry is obvious. A
suggestion is also made as to the efficacy of drying fish, even without
salt, the drying being complete to the exclusion of even hydroscopic
water, for the use of the explorer and traveller.
The inference as to the salutary effects of fish depending on the
presence of iodine, in the prevention of tubercular disease, might
be extended to _goitre_, which it is known has already yielded to
iodine. This formidable complaint appears to be completely unknown to
the inhabitants of sea-ports and sea-coasts. Respecting another and
concluding question, viz., the different parts of fish, it is to be
remarked that, so far as experiments have gone, the effects will not
be the same from all parts of the fish, because the inorganic elements
are not the same. The examples chosen are the liver, muscle, roe, or
melt. In the ash of the liver and muscle of sea-fish, Dr. Davy always
found a large proportion of saline matter, common salt, abounding,
with a minute portion of iodine, rather more in the liver than the
muscle, and free alkali, or alkali in a state to occasion an alkaline
reaction, as denoted by test-paper; whilst in the roe or melt there has
been detected very little saline matter, no trace of iodine, nor of
free alkali; on the contrary, a free acid, viz., phosphorus, analogous
to what occurs in the yolk of an egg, and in consequence of which it
is very difficult to digest either the roe or melt of a fish, or the
yolk of an egg. The same conclusion on the same ground is applicable to
fresh-water fish, viz., the absence of iodine.