2114. Several vertebræ are, however, found for the sense of feeling or touch, because it includes all the organs of the trunk. There must be therefore as many vertebræ in the trunk as there are particular organs placed therein. Of these there are three, the respiratory, digestive, and sexual system, or thorax, abdomen, and pelvis. To the thorax belong the neck, the arms, and the entire set of ribs. 5 vertebræ must appertain to the arms, because they have 5 digits and 5 nerves. But the ribs, and consequently also the digits, are determined by branchial vessels, are only repeated branchial arches, whose number in almost the entire class of fishes is 5. There are therefore also 5 thoracic or pulmonic vertebræ. Since the larynx consists of the 5 original branchial arches, and lies in front of the neck; so must the 5 superior cervical vertebræ stand in the signification of branchial vertebræ. The odontoid process of the second vertebra must be regarded, from its being separated from it in the fœtus, as a particular cervical vertebra. Accordingly, in the Thricozoa there are eight cervical vertebræ. The 3 inferior cervical, and the 2 upper costal or rib-vertebræ, give off through their interspaces the nerves of the arms, and are consequently the brachial vertebræ. The 3-7th rib are thus appended to the 5 proper thoracic vertebræ, which stand in the signification of the pulmonary vertebræ. To these succeed the 5 short ribs which belong to the abdomen; their vertebræ are thus intestinal vertebræ. The succeeding vertebræ belong to the sexual system, and are indeed the 5 lumbar or pedal vertebræ, because they furnish the pedal or foot-nerves, the 5 sacral vertebræ being the proper sexual vertebræ. The coccygeal or caudal vertebræ correspond to the cervical vertebræ, and are present for the sake of the sexual branchiæ; usually one and the other is arrested. Thus there are,—

3×5 Respiratory vertebræ.
3×5 Sexual vertebræ.
1×5 Digestive vertebræ.

The number of the sensitive vertebræ is consequently 7×5=35, which are distributed into three groups, in accordance with the principal cavities of the body, whereof the 2 terminal groups consist of 15, but the abdominal group, which combines or unites them, only of 5. The body is accordingly not merely laterally, but also in length, a perfectly symmetrical structure, which has been parcelled out in the following manner into its five stockworks, stories or floors:

I.Dermal vertebra.
A. Sexual vertebræ.
a. Coccygeal vertebræ5,
b. Sexual vertebræ5,
c. Pedal vertebræ5.
B. Abdominal vertebræ5.
C. Thoracic vertebræ.
a. Pulmonary vertebræ5,
b. Brachial vertebræ5,
c. Cervical vertebræ5.
II.Auditory vertebra1.
III.Lingual vertebra1.
IV.Optic vertebra1.
V.Nasal vertebra1.

This regularity is found too only in the human skeleton. The animals are irregular men. (Vide Oken's Zahlengesetz in den Wirbeln. Isis, 1829, S. 306.)

Cavities of the Trunk.

2115. The osseous system forms the trunk or body, because it follows the vascular system; the two other galvanic systems, the dermal and intestinal systems, form the large portions of the trunk or its cavities; to them is added the sexual cavity or pelvis.

2116. There are thus three truncal cavities, a pulmonary, an intestinal, and a sexual cavity, or thoracic, abdominal, and pelvic cavity.

2117. The osseous system will develop itself most feebly around the abdominal, because it is the indifferent cavity. Therefore there are either no ribs at all, or they are so short that they do not reach to the anterior vertebral column or the sternum. The short or false ribs are, according to their physiological sense, abdominal or splanchnic ribs. The thoracic ribs must be perfectly developed, i. e. abut against both vertebral columns, be entire ribs; the entire or perfect ribs are thoracic or pulmonary ribs. The sexual ribs are arrested on the pedal and coccygeal vertebræ, but on the proper sexual vertebræ, namely, the sacral bone, they are still present as rudiments.

3. MUSCULAR SYSTEM.