COROLLARIES from the above FACTS and EXPERIMENTS.
From the above Facts and Experiments, it appears,
1. That the Frog, after its Head is cut off, feels pain, and, in consequence of feeling, moves its Body and Limbs.
2. As the Nerves of the hind Legs are not affected by Animal Electricity, unless it be applied lower than the fifth Vertebra, these Nerves do not seem to be derived solely or chiefly from the Brain or Cerebellum.
3. As Opium, after the Circulation ceases, affects Organs distant from those to which it is applied, it is beyond doubt, that the latter suffer in consequence of Sympathy of Nerves.
4. It appears that, in this Animal, there is Sympathy of Nerves after the Head is cut off; or that Sympathy of Nerves does not, in this Animal, depend entirely on the connection of Nerves within the Head.
5. As, after cutting off the Head, this Animal is susceptible of pain, and, in consequence of that, performs voluntary motion, it appears that, in it, the Brain is not the sole seat of the Sensorium Commune.
6. Several weeks after I had taken out the lowermost half of the Spinal Marrow, and with it the Cauda Equina, I daily applied, for four days running, Animal Electricity to the Sciatic Nerves, by passing a gold Probe between them and the Os Sacrum, and excited several hundreds of convulsions of the Thighs and Legs, and yet found that, on laying bare the Femoral Nerves, and pinching them, the Muscles were slightly convulsed.
Hence, I apprehend, additional force is given to an opinion I ventured many years ago to propose[3], that the Nerves do not receive their energy wholly from the Head and Spinal Marrow, but that the texture of every branch of a Nerve is such as to furnish it, or that the structure of each Nerve is similar to that of the Brain.
7. From the above Experiments, it appears probable, in the highest degree, that Opium may be absorbed in such quantity as to produce fatal symptoms.
8. The following circumstances concur in rendering inadmissible an opinion lately proposed by M. Fontana, that Poisons operate by changes they produce on the mass of Blood, or on some unknown principle connected with the Blood.
a. If his opinion was just, Poison introduced into a Vein of the extremities, so as to be in contact with this unknown principle, should operate as quickly, and in the same manner as when the Poison is mixed with the Blood near the Heart, which he admits is not the case[4].
b. Cutting the Spinal Marrow in Frogs, before applying the Poison of the Viper to their Legs, prevents it from killing them[5]; which should not happen, if the Poison acted on the Blood alone.
c. He acknowledges that an Animal bit in its Leg by a 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.