85. The march of Cato from Berenice, in the province of
Cyrene, was much longer than that of Heraclius from Tripoli.
He passed the deep sandy desert in thirty days, and it was
found necessary to provide, besides the ordinary supplies, a
great number of skins filled with water, and several
'Psylli', who were supposed to possess the art of sucking
the wounds which had been made by the serpents of their
native country. See Plutarch in Caton. Uticens. [c. 56] tom.
iv. p. 275; Strabon. Geograph. 1. xvii. p. 1193 [p. 836, ed.
Casaub.].