The longitudinal body zones appear as approximately equal vertical fields, lined up in a medial to lateral direction from zone 1 to 5, respectively. Thereby, W. FitzGerald discovered a useful key for showing the correlations between the whole person and the foot in a pictorial and practically understandable manner:

The organs, tissues, and systems through which a longitudinal zone passes in the body are represented in the same longitudinal zone on the feet, reduced in proportion. The following examples illustrate this:

• The eyes are in body zones 2 and 3 with their related zones on the second and third toes.

• The hip joints belong to body zone 4 and are in the same longitudinal body zone on the feet, that is, close to the lateral malleolus.

All bilateral organs and joints (e.g. kidneys, ears, and shoulders) are represented on the right and left foot.

The zones of unilateral organs are on the same side as in the body (e.g., the zone of the spleen is on the left foot while the zones of the appendix and gall bladder are on the right foot).

Organs located in the center of the body have their corresponding zone in the center of the pair of feet, that is, in the respectively assigned longitudinal zone on the right and left foot (e.g., heart, stomach, and bladder).

In addition to the vertical 10-zone division, from 1967 onward a further distinction was made possible by three horizontal lines:

• The first horizontal line passes in situ to the right and left of the sternum over the clavicle at shoulder height and demarcates the areas of the head and neck. Transferred to the foot, this line passes through the 10 metatarsophalangeal joints and thus identifies the toes as being assigned to the head and neck.

• The second horizontal line roughly corresponds in situ to the waistline, is found at the base of the metatarsal bones in the feet and is known as the Lisfranc line. The organs of the thorax and upper abdomen are arranged between the first and second horizontal line in both the body and the feet.

• A third horizontal line corresponds in situ to the demarcation of the trunk from the lower extremities and is shown on the feet by a connecting line between the outer and inner malleoli. The reflex zones of the stomach and pelvic organs are found in the resulting area.

With this reciprocal assignment of the macrosystem to the person and microsystem to the foot, like placing a piece in a mosaic, it is easy to find the location or projection of the individual organs with the help of the longitudinal and horizontal grid.