THE original conception of an arrangement of the various parts of the abdominal alimentary tube within fixed ana- tomical boundaries, was completely disproved when it became possible to obtain radioscopie views of the alimentary tube in the living subject. From these it was apparent that only a few regions of the bowel could be regarded as even relatively fixed; the variations in position of the other parts were extremely marked. The relatively fixed regions are: (1) The region of the œsophageogastric orifice; (2) Practically the whole duodenum; (3) T h e region of the ileocecalorifice; (4) T h e ascending colon and the right colic flexure; (5) T h e left colic flexure and the descending colon; (6) The termination of the pelvic colon; and (7) T h e rectum. The remaining portions of the abdominal alimentary tube are mobile, some of them extremely so, and their positions at any one time are the resultant of various influences (a) in the bowel wall itself, (b) in the surrounding viscera, and (c) in the supporting abdominal walls.
The viscus on which most attention is focused is the stomach, and some further consideration m a y b e given to this. T h e general shape of the stomach is determined in the first instance by the tonus of its muscular walls. Speaking generally, there are two well-defined types. In the hypertonic type, which is usually associated with the hypertonic (hypersthenic) type of individual, the stomach is of the small steer-horn form, with firm walls (Fig. 13). The other type (orthotonic) is the J-shaped or ‘fish-hook’ form of stomach; an exaggerated form of this is often found in hypotonic (hyposthenic or asthenic) individuals (Figs. 1 4 A , 1 4 B ) . These tw o latter types are of larger size than the previous type, and have less firm walls.
In all these forms the fixed points are the cardiac orifice of the stomach and an area of the proximal part of the duodenum about 1 in . from th e pylorus. T h e short meso- gastrium (lesser omentum) between these points somewhat restricts the mobility of the lesser curvature and the pyloric ring, but the greater curvature is less limited and can be moved through a considerable arc to the left and downwards.
The stomach lies on a group of practically fixed structures (pancreas, kidney, etc.) on the posterior abdominal wall, and on a movable shelf formed by the transverse colon and its mesocolon (Fig. 15). This shelf rests on the coils of the small intestine and these are constantly undergoing changes in form and position. Overlying the stomach is a consider- able part of the liver and the diaphragm.
The disposition of all the movable viscera within the abdominal cavity is influenced by the muscular walls that enclose and control the size of the cavity, namely, the thoracic diaphragm above, the anterolateral abdominal muscles, and the pelvic diaphragm below. In studying the positions of the stomach, therefore, it is important to consider the state o f these muscles.
In the hypertonic individual the muscles exhibit a high degree of cellular tonus and therefore can respond rapidly and strongly to any calls on their activity. As a result, general body posture is good, so that in the erect position the anterior abdominal wall is flat, the thoracic diaphragm is high, and the lower aperture of the thorax is wide and deep.
Radioscopie examination shows the transverse colon high up in the abdominal cavity (probably above the umbilicus) and the mesocolic shelf approaching the horizontal. The small steer-horn stomach may be well under cover of the wide lower thorax.
In the hypotonic individual the more relaxed abdominal and pelvic muscles allow a sagging of the transverse shelf. The transverse colon may be found in the pelvis, and, in extreme cases, the lowest part of the J-shaped stomach is well below the umbilicus and it also may reach the pelvis. The thoracic diaphragm drops to a lower level and the lower thorax is long and narrow.
Special note may be made of the fact that in all these positions the fundus of the stomach remains in contact with the diaphragm.
It must be emphasized, however, that whatever be the form of the stomach, its position may be greatly modified by some of the other factors enumerated. Further, it may be pointed out that any of the above positions are compatible with normal functioning of the stomach.
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