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Internal Organs

inches, fish, stomach, liver and intestine

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INTERNAL ORGANS.

Of no less interest than the structures just described are the internal organs. Of fish No. 10 (3 feet 10 inches in extreme length) careful dissection and full notes were made. The abdominal cavity was 18.5 inches long from the diaphragm to the anus, with a 1-inch post-anal extension to be described later.

There seems to be in this fish a structure apart from the pericardial sac which functions as a true diaphragm. Cuvier and Valenciennes (1829) speak of a diaphragm in the European form, the spet. Con tained in the body-cavity were the spermaries, the air-bladder, and the alimentary tract with the liver and spleen. The digestive apparatus was 29.5 inches long, of which the stomach was 12.5 inches long by 1.5 inches wide, and the intestine 17 inches long by 0.5 inches wide. The stomach had the shape shown in text-figure 4 A, the intestine coming off 2.5 inches below or behind the oesophageal constriction. The sac below the pyloric opening was filled with the bones of fishes. My notes say that this organ was supplied with three large blood vessels, but their connections were not worked out.

When the abdomen is opened the first organ visible in the anterior end is the liver. This is shaped very like a flat or English riding saddle turned upside down, the "skirts" or flaps extending upwards on each side of the stomach. It lies in the extreme forward end of the abdomen just behind the heart. In specimen No. 10 it was just about an inch thick at the forward end, where it was thickest (the point marked x in the diagram, text-figure 4s). On the dorsal surface, opposite the point marked x, the bile duct, 3.5 inches long, was given off. This extended back to the gall bladder, which lay alongside the small intestine just anterior to the spleen. The gall bladder was 2 inches long and 0.5 inch wide, and was shaped somewhat like two con ventionalized wings placed base to base, as shown in the diagrammatic figure 4 c. The spleen had the same general shape, but was 3.25 inches long by 1 inch wide.

Lying between the body of the liver and the upturned "skirts" of the saddle (which were placed against the lateral walls of the abdomen) was the great mass of the pyloric caeca, which mass was shaped much like the liver, but had a greater volume and occupied a greater area.

Of these caeca, only those lying on the dorsal and ventral surfaces of the mass were counted, but even these numbered 148. Dorsal to this mass of caeca were the stomach and small intestine.

The dorsal part of the abdominal cavity is occupied by the much elongated air-bladder. Anteriorly this is bifurcated to form two horns, posteriorly there is but one which occupies the short post-anal exten sion of the abdomen (this was 1 inch long in a 3-foot 10-inch specimen). A fish 2 feet 10 inches in extreme length had an air-bladder 11.5 inches long, the anterior end of which had a 2.5-inch bifurcation. In a a foot 7-inch specimen, the air-bladder measured 15 inches, the horns being 3.5 inches in length. A third specimen, measuring 3 feet 10 inches between perpendiculars, had in its 18.5-inch abdominal cavity a 16.5-inch air-bladder, the bifurcation of which extended forward 3.5 inches. The general shape and appearance of this organ is shown in text-figure 4 D.

While dissecting this fish, some hard object was found embedded in the mesentery. At first it was thought that it was a mummified pipe fish, but when freed of all attached material it was seen to be the back bone of a fish. This was confirmed when a portion of it was put under a microscope. It was fairly straight save at the upper end, where it was bent as is shown in text-figure 5. It is hard to conjecture just how this vertebral column could have worked its way out through the wall of the intestine into the mesentery. Inclusions, while not common, are not unknown. Some half dozen or more have been noted, but will not be considered here.

The first of the old writers to give any account of the internal organs of a Sphyrcena is Rondelet (1558). His brief statement concerning the spet of the Mediterranean is as follows: "It has a long stomach with several additions [caeca], the bowels are long, the liver whitish." Sloane (1707) briefly says that its stomach is "sack-fashioned," and that the ccecal appendages are very many.

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