The myelinization of the central nervous system of the American water snake (Natrix sipedon).
- 1The descending fibre tracts extending from the brain to the spinal cord (the medial longitudinal bundle, the reticulo-spinal and the direct vestibulo-spinal tracts) become medullated earlier than the afferent fibre paths from the spinal cord to the brain.
- 2In the brain stem the vestibular nerve, the direct vestibulo-spinal tract, medial longitudinal bundle, and reticulo-spinal fibres are medullated very early.
- 3The lateral lemniscus is medullated, and can be traced to the inferior corpora quadrigemina and nucleus isthmi, at a relatively early stage of Natrix sipedon.
- 4The tectal component of the dorsal tecto-bulbar fibre tract does not become medullated until quite late. The dorsal tecto-bulbar fibre tracts are medullated earlier than the ventral ones.
- 5The fibre tracts of the spinal cord, medulla, and midbrain in Natrix sipedon become medullated in the same order as those of the opossum and the cat. The phylogenetically most ancient fibre tracts become medullated sooner than the newer tracts.
- 6The order of medullation of the cranial nerves and fibre tracts in Natrix sipedon resembles that of amphibia.