Erasmus Darwin

“ The sense of touch is also liable to be deceived from the acquired habits of one part of it acting in the vicinity of another part of it. Thus if the middle finger be crossed over either of the fingers next to it, and a nut be felt by the two ends of the fingers so crossed at the same time, the nut appears as if it was two nuts. And lastly, the sense of touch is liable to be deceived by preconceived ideas; which we believe to be excited by external objects, even when we are awake. ”

“ So when any one's fingers are pressed on a benumbed limb, the sensation produced is less than it should be, judging from visible circumstances; we therefore conceive, that something intervened between the object and the sense, for it is felt as if a blanket was put between them ”

“ M. M. The method of cure is to increase our knowledge of the laws of nature, and our habit of comparing whatever ideas are presented to us with those known laws, and thus to counteract the fallacies of our senses, to emancipate ourselves from the false impressions which we have imbibed in our infancy, and to set the faculty of reason above that of imagination. ”

“ As the optic nerves at their entrance into the eyes are each of them as thick as a crow-quill, it appears that a great quantity of sensorial power is expended during the day in the perpetual activity of our sense of vision, besides that used in the motions of the eye-balls and eyelids; as much I suppose as is expended in the motions of our arms, which are supplied with nerves of about the same diameters. From hence we may conclude, that the light should be kept from patients in fevers with debility, to prevent the unnecessary exhaustion of the sensorial power. ”

“ Hence though they are liable to surprise, when their passing trains of ideas are dissevered by violent stimuli; yet are they not affected with wonder or astonishment at the novelty of objects; as they possess but in a very inferior degree, that voluntary power of comparing the present ideas with those previously acquired, which distinguishes mankind; and is termed analogical reasoning, when deliberatively exerted; and intuitive analogy, when used without our attention to it, and which always preserves our hourly trains of ideas consistent with truth and nature. ”

“ If a fish, immediately upon being taken out of the water, is stunned by a violent blow on the head, or by having the head crushed, the irritability and sweetness of the muscles will be preserved much longer, than if it had been allowed to die with the organs of sense entire. ”

“ Of this kind are the bulk of mankind; they continue throughout their lives in a state of childhood, and have thus been the dupes of priests and politicians in all countries and in all ages of the world.
In regard to religious matters, there is an intellectual cowardice instilled into the minds of the people from their infancy; which prevents their inquiry: credulity is made an indispensable virtue; to inquire or exert their reason in religious matters is denounced as sinful; and in the catholic church is punished with more severe penances than moral crimes. ”

“ Hence dark spots are seen on the bed-clothes by patients, when the optic nerve is become less irritable, as in fevers with great debility; and the patients are perpetually trying to pick them off with their fingers to discover what they are; for these parts of the retina of weak people are sooner exhausted by the stimulus of bright colours, and are longer in regaining their irritability. ”

“ Another exuberant source of error consists in the false notions, which we receive in our early years from the design or ignorance of our instructors, which affect all our future reasoning by their perpetual intrusions; as those habits of muscular actions of the face or limbs, which are called tricks, when contracted in infancy continue to the end of our lives. ”

“ Ignorance and credulity have ever been companions, and have misled and enslaved mankind; philosophy has in all ages endeavoured to oppose their progress, and to loosen the shackles they had imposed; philosophers have on this account been called unbelievers: unbelievers of what? ”

“ Other kinds of ocular spectra, as the coloured ones, are also more liable to remain in the eyes of people debilitated by fevers, and to produce various hallucinations of sight. For after the contraction of a muscle, the fibres of it continue in the last situation, till some antagonist muscles are exerted to retract them; whence, when any one is much exhausted by exercise, or by want of sleep, or in fevers, it is easier to let the fibres of the retina remain in their last situation, after having been stimulated into contraction, than to exert any antagonist fibres to replace them. ”

“ Squinting is generally owing to one eye being less perfect than the other; on which account the patient endeavours to hide the worst eye in the shadow of the nose, that his vision by the other may not be confused. ”

“ When the motions of the fibrous extremities of the nerves of sense are too weak to excite sensation with sufficient quickness and vigour. The irritative ideas are nevertheless performed, though perhaps in a feeble manner, as such people do not run against a post, or walk into a well. ”

“ In this last case the minute parts of an object, as suppose of a distant boy, are seen less distinctly, and therefore we instantly conceive them to be further from the eye, and in consequence that the whole subtends a larger angle, and thus we believe the boy to be a man. ”

“ In our approach to old age our vision becomes imperfect, not only from the form of the cornea, which becomes less convex, and from its decreased transparency mentioned in Class I. 2. 3. 26.; but also from the decreased irritability of the optic nerve. Thus, in the inirritative or nervous fever, the pupil of the eye becomes dilated; which in this, as well as in the dropsy of the brain, is generally a fatal symptom. A part of the cornea as well as a part of the albuginea in these fevers is frequently seen during sleep ”

“ Is a blindness from the inirritability of the optic nerve. It is generally esteemed a palsy of the nerve, but should rather be deemed the death of it, as paralysis has generally been applied to a deprivation only of voluntary power. ”

“ Thus if a person is said to have received the small-pox a second time, and to have gone through all the stages of it, one may thus reason: twenty thousand people have been exposed to the variolous contagion a second time without receiving the variolous fever, to every one who has been said to have thus received it ”

“ In inflammatory or sensitive fevers with debility, deafness may sometimes arise from a greater secretion and absorption of the ear-wax, which is very similar to the bile, and is liable to fill the meatus auditorius, when it is too viscid, as bile obstructs the gall-ducts. ”

“ But in respect to our belief of the supposed medical facts, which are published by variety of authors; many of whom are ignorant, and therefore credulous; the golden rule of David Hume may be applied with great advantage. "When two miraculous assertions oppose each other, believe the less miraculous." ”

“ Dark spots appearing before the eyes, and changing their apparent place with the motions of the eyes, are owing to a temporary defect of irritability of those parts of the retina, which have been lately exposed to more luminous objects than the other parts of it, as explained in Sect. ”

“ Or the better eye should be totally darkened by a tin cup covered with black silk for some hours daily, by which means the better eye will be gradually weakened by the want of use, and the worse eye will be gradually strengthened by using it. Covering an inflamed eye in children for weeks together, is very liable to produce squinting, for the same reason. ”

“ At the commencement of this disease, very minute electric shocks should be repeatedly passed through the eyes; such as may be produced by putting one edge of a piece of silver the size of a half-crown piece beneath the tongue, and one edge of a piece of zinc of a similar size between the upper lip and the gum, and then repeatedly bringing their exterior edges into contact, by which means very small electric sparks become visible in the eyes. ”

“ The absence of voluntary power and consequent incapacity to compare the ideas of present and future good. Brute animals may be said to be in this situation, as they are in general excited into action only by their present painful or pleasurable sensations. ”