The alligator and its allies

by A. M. Reese

The submucosa, sm, is of average thickness and density. In the fundic and cardiac regions it seems to extend between the circular and oblique layers; at any rate, there is a considerable layer of connective tissue between these two muscular layers.

The circular muscular layer, cm, is of only moderate thickness and is of rather a loose character. In the pyloric region it is not very distinct from the underlying oblique layer, but in the other regions, as has just been said, it is separated from the oblique layer by a considerable layer of connective tissue like that of the submucosa.

The oblique layer, om, even in this section of the pyloric region is the thickest of the three muscle layers; while in the cardiac, and especially in the fundic, regions it is of great thickness, as was noted above, and is made up of larger bundles with less intervening connective tissue.

Fig. 45. A transsection through the wall of the pyloric region of the stomach of the feeding animal, under low magnification; m, mucosa; om, oblique muscles; other letters as in [Figure 42].

The outer or longitudinal muscle layer, lm, is comparatively little developed and consists of small rather scattered bundles of muscles with a correspondingly large amount of connective tissue. This connective tissue passes insensibly into that of the surrounding serosa, s, a loose, vascular layer of varying thickness and density, shown very thick in [Figure 45], but often much thinner.

So far as could be determined, the mucous membrane has the same structure in both anterior and middle regions of the stomach. That of the pyloric or small region, although fixed, stained, et cetera, just as carefully as the rest, did not show cell details sufficiently well to draw; the ducts of the glands in this region are fairly distinct but the deeper parts of the glands have the appearance of series of alveoli or large adipose cells. What the significance of this condition may be the writer is not able to say, but since the structure of this region of the gastric mucous membrane is not clear no attempt will be made to describe its appearance under higher magnification than was employed in the [figure] above. However, as will be noted below, there is probably no great difference between the pyloric mucosa and that of the other regions of the stomach.

Fig. 46. The glands of the middle or fundic region of the stomach of the hibernating animal, under high magnification; A, through duct; B, through body of gland; C, through fundus of gland.

[Figure 46] shows portions of typical glands from the mucosa of the middle region of the stomach, the posterior border of the large stomach cavity; A is a longitudinal section through two ducts where they open to the surface; B is a similar section through the body of a gland below the region of the duct; C is a transsection through the bottom or fundus of a gland; all are drawn with a camera under the same magnification.