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I was induced to make two other very cruel experiments on different animals, by laying bare their [[ stroke through]] patella's of the knees : having cut off all the skin round about, I then pricked and touched with the afore-mentioned escharotics the capsular ligaments of these joints, without discovering any tokens of pain thereby occasioned; but as soon as the sharp fluids had spread over the surface, so as to reach the extremity of the skin, the creature underwent as much pain as cutting before had caused.
     I desired the butcher to take off as much skin from the forehead, as was necessary to perform the operation of the trepan; and before I began to apply the instrument to the sheep's forehead, I vellicated the pericranium with the end of a knife, but could not observe the membrane sensible, or thereby thrown into contractions; and when the operation was over, and the bone taken from the subjacent dura mater, I poured on this membrane dulcified spirit of nitre, and diluted spirit of vitriol, and powdered common salt, but without perceiving any agitations whatsoever, brought on by these substances acting upon these living parts; though in some creatures I am dubious, whether sea-salt and nitre in powder did not create in some sense, though no manifest contractions of the dura mater.
     But every muscular part, which I cut while the animals were alive, discovered little sensibility of pain, though great propensity to irregular spasms of the fibres: and the muscles upon the thorax, and especially the carned columna of the heart, retained irritability last of all other muscular parts, even till long after the animal's expiration.
     I laid the pungent liquors and salts, as above, upon various parts of the animal, yet alive; as upon the fat, cellular membrane of the neck, leg, and other parts within the skin, the liver, pancreas and spleen, and could not find them endowed either with remarkable sensibility or irritability; nor had the bladder any remarkable symptoms of irritability, farther than might be occasioned by its muscular fibres; though the well known symptoms of the calculus shew its great sensibility.
     I tried the effects of a strong aqueous solution of opium upon the irritated parts of muscular fibres, but could not perceive an opiate manifestly to compose these spastic motions of the parts, as Haller (who mentions most of these experiments in his late treatise entitled, [[underline]] A Dissertation upon the Irritability of animal fibres [[/underline]].) alleges they do: tho' in some trails I fancied there were grounds for such a conclusion. However this is no argument against the internal use of opiates, where the solids are greatly irritated.
     I must add one more experiment, which I made upon the intestines of a lamb: after I had taken them from the carcass, I poured diluted spirit of vitriol on them, as well as several other pungent substances; and upon the touch of all of them, the intestines renewed their contraction, which before had totally ceased, and surprised me with a motion almost as strong as is found in the process of [[chylification?]]; and this continued till the external cold had indurated and stiffened the fatty membrane of the comentum.
     These were some of many experiments of a like nature, which the importance of these facts in daily practice of medicine required to ascertain, or reject; and from the result of my repeated trials, I am induced to coincide with most of the conclusions drawn by Drs. Haller, Castell, and Zimmerman; that no part is sensible but the nerves only, and that some parts are irritable without sensibility accompanying them in any great degree; whilst others are altogether without sense, at the same time that they are incapable of being irritated at all."
New Broad-street
June 19, 1755

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