After a common degree of exhaustion of the sensorial power in a muscle, it becomes again gradually restored by the rest of the muscle; and even accumulated in those muscles, which are most frequently used; as in those which constitute the capillaries of the skin after having been rendered torpid by cold. But in those muscles, which are generally obedient to volition, as those of locomotion, though their usual quantity of sensorial power is restored by their quiescence, or in sleep (for sleep affects these parts of the system only), yet but little accumulation of it succeeds. And this want of accumulation of the sensorial power in these muscles, which are chiefly subservient to volition, explains to us one cause of their greater tendency to paralytic affection.
It must be observed, that those parts of the system, which have been for a time quiescent from want of stimulus, as the vessels of the skin, when exposed to cold, acquire an accumulation of sensorial power during their inactivity; but this does not happen at all, or in much less quantity, from their quiescence after great expenditure of sensorial power by a previous excessive stimulus, as after intoxication. In this case the muscles or organs of sense gradually acquire their natural quantity of sensorial power, as after sleep; but not an accumulation or superabundance of it. And by frequent repetitions of exhaustion by great stimulus, these vessels cease to acquire their whole natural quantity of sensorial power; as in the schirrous stomach, and schirrous liver, occasioned by the great and frequent stimulus of vinous spirit; which may properly be termed irritative paralysis of those parts of the system.
In the same manner in common palsies the inaction of the paralytic muscle seems not to be owing to defect of the stimulus of the will, but to exhaustion of sensorial power. Whence it frequently follows great exertion, as in Sect. XXXIV. 1. 7. Thus some parts of the system may cease to obey the will, as in common paralysis; others may cease to be obedient to sensation, as in the impotency of age; others to irritation, as in schirrous viscera; and others to association, as in impediment of speech; yet though all these may become inexcitable, or dead, in respect to that kind of stimulus, which has previously exhausted them, whether of volition, or sensation, or irritation, or association, they may still in many cases be excited by the others.
SPECIES.
[1]. Lassitudo. Fatigue or weariness after much voluntary exertion. From the too great expenditure of sensorial power the muscles are with difficulty brought again into voluntary contraction; and seem to require a greater quantity or energy of volition for this purpose. At the same time they still remain obedient to the stimulus of agreeable sensation, as appears in tired dancers finding a renovation of their aptitude to motion on the acquisition of an agreeable partner; or from a tired child riding on a gold-headed cane, as in Sect. XXXIV. 2. 6. These muscles are likewise still obedient to the sensorial power of association, because the motions, when thus excited, are performed in their designed directions, and are not broken into variety of gesticulation, as in St. Vitus's dance.
A lassitude likewise frequently occurs with yawning at the beginning of ague-fits; where the production of sensorial power in the brain is less than its expenditure. For in this case the torpor may either originate in the brain, or the torpor of some distant parts of the system may by sympathy affect the brain, though in a less proportionate degree than the parts primarily affected.
[2]. Vacillatio senilis. Some elderly people acquire a see-saw motion of their bodies from one side to the other, as they sit, like the oscillation of a pendulum. By these motions the muscles, which preserve the perpendicularity of the body, are alternately quiescent, and exerted; and are thus less liable to fatigue or exhaustion. This therefore resembles the tremors of old people above mentioned, and not those spasmodic movements of the face or limbs, which are called tricks, described in Class [IV. 1. 3. 2]. which originate from excess of sensorial power, or from efforts to relieve disagreeable sensation, and are afterwards continued by habit.
[3]. Tremor senilis. Tremor of old age consists of a perpetual trembling of the hands, or of the head, or of other muscles, when they are exerted; and is erroneously called paralytic; and seems owing to the small quantity of animal power residing in the muscular fibres. These tremors only exist when the affected muscles are excited into action, as in lifting a glass to the mouth, or in writing, or in keeping the body upright; and cease again, when no voluntary exertion is attempted, as in lying down. Hence these tremors evidently originate from the too quick exhaustion of the lessened quantity of the spirit of animation. So many people tremble from fear or anger, when too great a part of the sensorial power is exerted on the organs of sense, so as to deprive the muscles, which support the body erect, of their due quantity.
[4]. Brachiorum paralysis. A numbness of the arms is a frequent symptom in hydrops thoracis, as explained in Class [I. 2. 3. 14]. and in Sect. XXIX. 5. 2.; it also accompanies the asthma dolorificum, Class [III. 1. 1. 11]. and is owing probably to the same cause in both. In the colica saturnina a paralysis affects the wrists, as appears on the patient extending his arm horizontally with the palm downwards, and is often attended with a tumor on the carpal or metacarpal bones. See Class [IV. 1. 2. 10].
Mr. M——, a miner and well-sinker, about three years ago, lost the power of contracting both his thumbs; the balls or muscles of the thumbs are much emaciated, and remain paralytic. He ascribes his disease to immersing his hands too long in cold water in the execution of his business. He says his hands had frequently been much benumbed before, so that he could not without difficulty clench them; but that they recovered their motion, as soon as they began to glow, after he had dried and covered them.