In order to proceed with the second and third methods of preserving fish specimens, it now becomes necessary to describe a process.
HOW TO SKIN A FISH.--Of course, no one aspiring to become a collector of fishes will remain in ignorance of the names of the different fins. And, more than that, before he can prepare even the rough skeleton of a fish he must know what its bony structure is like. On the whole, there is a good deal to be learned about methods in collecting fishes, and as a beginning we must learn how to skin a scale fish. The methods with cartilaginous fishes will be considered later.
The principles with all scale fishes are precisely the same, the only difference being in the greater amount of cold steel and energy required for such great, hulking brutes as the jewfish, and the magnificent tarpon. For convenience we will take a specimen about a foot in length; for example, a striped bass, a pike, or a red snapper.
As is the case with quadrupeds, the left side of a mounted fish is always expected to be "the show side." Lay the specimen upon its left side, start at the vent with a stout pair of sharp-pointed scissors, and divide the skin in a perfectly straight line along the median line of the belly toward the head, stopping the cut when you approach close to the narrow, tongue-like point which terminates between the lower angles of the gill openings. Now reverse the fish, begin again at the vent, and divide the skin with a clean cut through the scales, in a line parallel with the base of the anal fin, and about half an inch from where the scales meet the fin rays. This is really a cut along the side of the fish, as low down as possible, made necessary by reason of the anal fin. Continue this cut straight back to the tail, as shown in the dotted line _g-h_ in Plate IV.
[Illustration: PLATE IV. HOW TO CUT OPEN AND MOUNT A FISH.]
You will find that the ventral fins are joined together in the flesh by a strong bony arch, called the pubis, and this must be divided through the middle so as to entirely separate the fins. The anal fin-rays must now be cut loose from the interior rays (called interhæmal spines), which are really their bony foundation. The ventral fins must also be cut loose from the pubic bones at the point where they are articulated. Now take the cut edge of the fish skin between the left thumb and forefinger, and with the cartilage-knife carefully cut the skin free from the flesh. Be careful not to disturb the white layer of color pigment which is spread like a silver lining of feeble tin-foil over the inside of the skin. This is what gives the fish its silvery color, and if skinned off or scraped away the skin will look like colorless parchment. _Whatever you do, do not disturb that color lining._ Proceed with the skinning until the skin has been detached from the entire upper side of the fish. This brings you to where the dorsal and caudal fins are inserted.[6]