[11]. Consternatio. Surprise. As our eyes acquaint us at the same time with less than half of the objects, which surround us, we have learned to confide much in the organ of hearing to warn us of approaching dangers. Hence it happens, that if any sound strikes us, which we cannot immediately account for, our fears are instantly alarmed. Thus in great debility of body, the loud clapping of a door, or the fall of a fire-shovel, produces alarm, and sometimes even convulsions; the same occurs from unexpected sights, and in the dark from unexpected objects of touch.
In these cases the irritability is less than natural, though it is erroneously supposed to be greater; and the mind is busied in exciting a train of ideas inattentive to external objects; when this train of ideas is dissevered by any unexpected stimulus, surprise is excited; as explained in Sect. XVII. 3. 7. and XVIII. 17. then as the sensibility in these cases is greater, fear becomes superadded to the surprise; and convulsions in consequence of the pain of fear. See Sect. XIX. 2.
The proximate cause of surprise is the increased irritation induced by some violent stimulus, which dissevers our usual trains of ideas; but in diseases of inirritability the frequent starting or surprise from sounds not uncommon, but rather louder than usual, as the clapping of a door, shews, that the attention of the patient to a train of sensitive ideas was previously stronger than natural, and indicates an incipient delirium; which is therefore worth attending to in febrile diseases.
ORDO [II].
Decreased Irritation.
GENUS [I].
With decreased Action of the Sanguiferous System.
The reader should be here apprized, that the words strength and debility, when applied to animal motions, may properly express the quantity of resistance such motions may overcome; but that, when they are applied to mean the susceptibility or insusceptibility of animal fibres to motion, they become metaphorical terms; as in Sect. XII. 2. 1. and would be better expressed by the words activity and inactivity.
There are three sources of animal inactivity; first, the defect of the natural quantity of stimulus on those fibres, which have been accustomed to perpetual stimulus; as the arterial and secerning systems. When their accustomed stimulus is for a while intermitted, as when snow is applied to the skin of the hands, an accumulation of sensorial power is produced; and then a degree of stimulus, as of heat, somewhat greater than that at present applied, though much less than the natural quantity, excites the vessels of the skin into violent action. We must observe, that a deficiency of stimulus in those fibres, which are not subject to perpetual stimulus, as the locomotive muscles, is not succeeded by accumulation of sensorial power; these therefore are more liable to become permanently inactive after a diminution of stimulus; as in strokes of the palsy, this may be called inactivity from defect of stimulus.