Masses of nerve tissue are called ganglia (singular: ganglion).

Here's a breakdown:

* Ganglia: These are collections of neuron cell bodies located outside of the central nervous system (brain and spinal cord). They act as relay stations for nerve impulses, processing information before it is sent to the brain.

* Nerves: These are bundles of axons (the long projections of neurons) that transmit signals throughout the body. They are not collections of cell bodies like ganglia.

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