ABSTRACT
As in the crustaceans and insects, so in the scorpion the primary afferent fibres constitute a considerable proportion of the axons in the central connectives.
The possibility of a sensory neurone sending collaterals, while passing through a ganglion, which activate a contralateral interneurone has been conclusively demonstrated. This type of activation differs from the pattern of contralateral activation so far demonstrated in the insects and crustaceans. In the latter groups, the available evidence indicates the activation of contralateral interneurones by the terminal branches of the sensory axons, but not by the collaterals.
It has been emphasized that in the scorpion, but not in insects and crustaceans, the tactile input from a single hair is adequate to trigger the central responses, which in itself is an advantage in analysing the integrative processes and functional connexions between neurones.
