nerve cord

noun

a single hollow tract of nervous tissue that constitutes the central nervous system of chordates and develops into the spinal cord and brain in vertebrates.
a solid double strand of nerve fibers along the length of the body in elongate invertebrates, as earthworms and insects, connecting with a pair of nerve ganglia at each body segment.

First recorded in 1875–80

In specimens with the proboscis drawn in, the nerve cord is of course doubled back on itself.

Earlier than that, in 1839, Nasse had discovered that a severed nerve cord degenerates in its peripheral portions.

But Helmholtz readily demonstrated the contrary, showing that the nerve cord is a relatively sluggish message-bearer.

Some became greatly elongated, and had developed so that the thread surrounded the dorsal nerve-cord.

The notochord is enclosed in a thick sheath of connective tissue continuous with a thinner sheath round the nerve cord.

April 19, 2024tortuous

[tawr-choo-uhs ]

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