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قراءة كتاب Experiments on the Nervous System with Opium and Metalline Substances Made Chiefly with the view of Determining the Nature
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Experiments on the Nervous System with Opium and Metalline Substances Made Chiefly with the view of Determining the Nature
Viper, instantaneously feels acute pain[6]; and it, in like manner, feels instantly great uneasiness when the Poison is mixed with its Blood[7]. We know for certain, that, through the medium of the Nerves, we are instantly rendered sensible of injury done to the most distant parts of our Bodies.
Are we not, therefore, in the last mentioned Experiment, to conclude, that the uneasiness was produced because the Poison acted upon the Nerves of the Vessels?
d. In like manner, Animals were convulsed as soon as they were wounded, or received the Poison into a Blood-vessel; and long before the Blood could have reached the Muscles in action[8].
e. As soon as the distilled Water of Lauro-cerasus was poured into the Stomach of a Pigeon, it was convulsed, died instantly[9], that is, before the Poison could have entered the Mass of Blood.
f. Many years ago, I found, after cutting the Venæ Cavæ and Aorta of a Frog, that a watery solution of Opium poured into the Heart, occasioned, in a few minutes, convulsions in its Legs; and, after cutting out the Heart, that the Opium poured into the Cavity of the Abdomen affected the Legs in like manner; although, in these Experiments, the Circulation was not only interrupted, but the greater part of the Blood evacuated.
I therefore then concluded[10], and now conclude, that Opium and other Poisons, even after they are mixed with the Mass of Blood, produce their fatal effects, chiefly and almost solely, by acting on the Nerves of the Heart and Vascular System, and, through these, affecting the whole of the Nervous System.
SUMMARY of EXPERIMENTS made on ANIMALS with METALLINE SUBSTANCES.
I shall now proceed to state the several circumstances I have observed, in my Experiments, which more directly lead us to judge of the Nature and Cause of Animal Electricity.
1. When two Plates of different Metalline Substances, particularly of Zinc and Gold, between which a living Frog is placed, are brought into contact with each other, those Muscles, which are farther from the Brain and Spinal Marrow than the Metals, are convulsed: and this effect follows, although the Animal and Metals are placed on an inverted glass jar, and that a stick of sealing wax is interposed between the hand of the Operator and the Metals; that is, although the Animal, with the Metals, be insulated.
I have further observed, that the Metals, disposed as above described, excite convulsions in the Legs, after all the parts of the Frog have been divided transversely at the Pelvis, providing only that they are, thereafter, laid in contact with each other.
2. When all the parts of a living Frog, except the large Nerves called Sciatic, are cut transversely at the Pelvis, and the fore part of the Animal is laid on a plate of Zinc, supported by glass, and the hind Legs on glass; if a gold Probe be applied so as to touch the Zinc and one of the Legs; or a piece of Metal put under one of the Legs; the Muscles of both Legs will be convulsed.
The event is the same, after the Body of the Frog has been cut transversely about the middle of the Spine: or when the Legs are laid on the Zinc and the Spine on Glass.
If a piece of perforated dry Paper is placed between the gold Probe and the Muscles, there will be no convulsions; but wet Paper interposed does not prevent the convulsions.
On separating the gold Probe from the Muscles there are no convulsions.
3. If, after the Animal and Metals are placed as above described, the joining of the two Legs at the Ossa Pubis is cut, that Leg only will be convulsed with which the gold is in contact.
4. The Spine of the Frog with the Zinc being placed on one glass, and the Legs on another glass, if the gold, supported by one hand, which we shall call the Right Hand, be applied to the Zinc alone, and not to the Legs, these are not convulsed. But if the Operator applies his left hand to the Legs, or if a bystander, communicating with the Operator by the medium of the floor only, touches them, they are convulsed. If a stick of sealing-wax be interposed between his right hand and the gold, or between his left hand and the Legs; or, if the bystander, touching the Legs, is insulated, by standing on a stool supported by glass feet, the Legs will not be convulsed. If the insulated bystander touches the Legs with one hand, and the Operator with his other hand, the Legs are immediately convulsed.
5. After cutting the Spine transversely under the fifth Vertebra, and all the parts of the Pelvis, except the Sciatic Nerves, and laying the Spine on Zinc supported by glass, and the Legs on glass; if gold be applied to the Zinc, and then to one of the Sciatic Nerves, both Legs, if they have not been separated from each other at the Ossa Pubis, will be convulsed[11]. And this happens although a stick of sealing-wax be interposed between the hand of the Operator and the gold Probe, and although no Metalline Substance touches the Legs.
This Experiment succeeds after denuding the Sciatic Nerves for the length of an inch, and wiping them dry; and it continues to succeed for an hour or more, and till the Nerves are evidently discoloured and shrunk in their size. And, after that, although we wet the Nerves, their powers are not restored; shewing that the influence had been conveyed not by wetness on the surface of the Nerves, but by the particular matter of which Nerves are composed.
The event is the same, when the upper ends of the Sciatic Nerves are cut away from the Spine, and laid on the Zinc.
6. After preparing the Frog and placing the Metals as in last Experiment, if a piece of thin dry Paper, pierced with a number of small holes, be interposed between the gold Probe and the Sciatic Nerves, the Legs will not be convulsed. But, if the Paper be wetted, although it is not perforated, the Legs will be convulsed.
After preparing a Frog, as in last Experiment, and laying the Spine on one glass, and the