ALIMENTARY TRACT OF THE KING SALMON 
77 
MUSCULAR WALL OF THE ESOPHAGUS. 
The muscular wall of the esophagus consists of a single circular coat. This is a 
thick, heavy muscular mass which is composed wholly of striated fibers. These fibers 
are about 15 // in diameter. Their length was not determined, but they are relatively 
long. Numerous nuclei are found along every fiber, each nucleus lying just within the 
sarcolemma. The nuclei of the striated fibers are oval, but vary considerably in shape 
and size, averaging 6 by 9 /x. The total thickness of the circular muscle coat amounts 
to about 200 /X in a young salmon 7 cm. long in which these measurements were made. 
In the adult fish of course the total mass of the muscle is very much greater. 
SEROUS COAT. 
The posterior end of the esophagus where it passes over into the stomach is free 
and therefore covered with a serous coat. The serous epithelial cells covering this coat 
are very thin, and are of the usual stratified type. No thick subserous connective 
tissue which characterizes the intestine and caeca was noted in the esophagus. It was 
noted, however, that numerous blood vessels are present just under the serous coat. 
This vascular factor characterizes the esophagus in all the salmon studied. 
THE STOMACH. 
FORM AND DIVISIONS OF THE STOMACH. 
The stomach of the king salmon is a U-shaped organ. The first limb of the U 
extends from the esophagus straight posteriorly a distance equivalent to one-fourth 
the length of the fish. At this point the stomach makes a sharp bend and extends 
directly back toward the head for about one-third the length of the first division. In 
the adult the lengths of these divisions of the stomach vary in proportion to the total 
length of the fish, but in an average-sized salmon, 80 cm., the length of the first, or 
cardiac division is from 20 to 22 cm., and of the second or pyloric division, from 6 to 
7 cm. 
There is great variation in the size of the stomach in feeding salmon from Monterey 
Bay. In the market there are always individual fishes in which the stomachs are empty 
and contracted until the gastric cavity is obliterated, i. e., until the mucous folds are 
in contact and the cavity is a potential one only. In the empty condition the cardiac 
division of the stomach is a regular cylinder in form and shape. The contracted walls 
are firm and resistant to the touch, and the total diameter is reduced to 1.5 to 2 cm. 
The pyloric division is also contracted, is firm to the touch, and its diameter is a trifle 
less in any given salmon than that of the cardiac division. The mucosa is compressed 
into great longitudinal ridges or folds. When the stomach wall is split open for its 
full length and the cavity opened out, then these folds appear as prominent longitudinal 
ridges. 
If only a small amount of food is present in the stomach — ^for example, a single small 
fish or a squid — the mucous lining is pressed firmly against this food mass and the gross 
shape of the stomach is much the same as in the empty organ. But in these instances 
60289° — Bull. 32 — 14 6 
