Richard Whitekettle, «Rats are Like Snakes, and Hares are Like Goats: A Study in Israelite Land Animal Taxonomy», Vol. 82 (2001) 345-362
Israelite taxonomic thought drew a contrast between a land animal taxon referred to by the words Cr#$ or #&mr that contained animals such as rats and snakes (Land Animals I), and a land animal taxon referred to by the words hmhb or hyx that contained animals such as hares and goats (Land Animals II). This essay shows that the Land Animals I taxon was characterized by locomotory movement in the horizontal plane and the Land Animals II taxon was characterized by locomotory movement in the vertical plane. Thus, the contrast was between land animals that were perceived to move along the ground (Land Animals I) and land animals that were perceived to move over the ground (Land Animals II).
To summarize, the limb excursion and trunk movements of sprawling stance Land Animals occur largely along a horizontal plane relative to the ground; the limb excursion and trunk movements of upright stance Land Animals occur largely along a vertical plane relative to the ground29.
VI. The
Morphology and Kinematics
of Legless
Land Animal Locomotion
Turning now to legless Land Animals, the obvious morphological characteristic of these animals relevant to this study is the lack of any limbs that might generate movement. Consequently, such animals use their limbless bodies to generate movement.
Snails and slugs use two methods to move: ciliary action and muscular locomotory waves30. Propulsion by the beating of the cilia on the animal’s ‘foot’ results in a gliding motion. Muscular locomotory waves involve virtually imperceptible vertical undulations in the muscular tissue of the foot thereby sliding the animal forward. This is seen in the following lateral view of a snail31:
Note, that, whether the method is ciliary action or muscular waves, all or most of the ventral surface of the snail and slug remains in contact with the ground during movement, causing the dorsal surface of the animal to pass through space at a uniform height over the substrate. Note too, that, snails and slugs use lateral trunk bending in order to change their direction of movement32.