Quantum autem ad animalem motum appetitus, timor contractionem quandam importat, quia timor provenit ex phantasia alicuius mali imminentis quod difficile repelli potest, ut supra dictum est; quod autem aliquid difficile possit repelli, provenit ex debilitate virtutis, ut supra dictum est; virtus autem, quanto est debilior, tanto ad pauciora se potest extendere: et ideo ex ipsa imaginatione quae causat timorem, sequitur quaedam contractio in appetitu.
As to the appetitive movement of the soul, fear implies a certain contraction, because fear arises from the imagination of some threatening evil which is difficult to repel, as stated above (q41 a2); but that a thing be difficult to repel is due to lack of power, as stated above (q43 a2); and the weaker a power is, the fewer the things to which it extends: wherefore from the very imagination that causes fear there ensues a certain contraction in the appetite.
In passionibus animae est sicut formale ipse motus appetitivae potentiae, sicut autem materiale transmutatio corporalis, quorum unum alteri proportionatur. Unde secundum similitudinem et rationem appetitivi motus, sequitur corporalis transmutatio.
In the passions of the soul, the formal element is the movement of the appetitive power, while the bodily transmutation is the material element. Both of these are mutually proportionate; and consequently the bodily transmutation assumes a resemblance to—and the formal aspect of—the appetitive movement.
Damascenus dicit, in III libro, quod timor est virtus secundum systolen, idest secundum contractionem.
Damascene says (De Fide Orth. ii, 23) that "fear is a power according to systole," i.e. contraction.
Et inde est quod timentes mortem pallescunt, ut dicitur in IV Ethic.
Hence it is that "those who are in fear of death turn pale" (Ethic. iv, 9).