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“Plants are beings so analogous to animals, that he may be excused who has defined them rooted animals. In the works of Vallisneri, Buffon, Bonnet, and, lasty, of the abbé Corti, may be seen the numerous and various traits of analogy between these two classes of organised beings. The subject of which we treat presents a new analogy: for as different animals revive after death, so do many plants spring again after they have perished. It would be departing from my plan, was I to say as much of them as I have said of animals; and 1 shall be content with mentioning two, the nostoc and tremella. The nostoc, so named by Paracelsus, is a terrestrial plant, whose sudden appearance in places where there was no sign of it before was considered by the ancients rather as a prodigy of heaven or earth than as a plant. Thus they denominated it heaven's jlower and earth's flower. It is seen in all seasons, but particularly in summer, after heavy rains. Though it springs in every soil, it prefers meadows, arid lands, and sandy valleys. The colour is a brownish green, the figure irregular, and resembling a leaf carelessly folded. When separated with the fingers, some resistance is felt, such as one feels on tearing a young leaf. If a sudden drought happens, the nostoc contracts and dries, remaining only a shrivelled, fines thin skin. If a sudden and heavy rain falls, it again becomes green, and resumes its original size. Therefore the nostoc, as Réaumur, who has furnished me with this intelligence, observes, is a plant of a singular kind, since it recovers life after being in a state which to others would be permanent death.

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visible at the sides and the bottom, which the microscope shewed me consisted of the tremella, dry and dead. “What can be the reason why these animals and plants are thus privileged, in comparison to many others which, perishing once, perish for ever?—Shall we perhaps ascribe it to the simplicity of their structure ? But this opinion or conjecture does net seem well founded. There are many animals that never revive, whose structure is as simple, or even more so, than that of the resurgent animals. Are not many infusion animalcula, which are composed of a simple aggregate of vesicles, undoubtedly less complex than wheel animals, which are provided with vessels, wheels, intestimes, and ovaries? Yet they do not recover life when once it is lost. Simplicity of structure would even seem an obstacle to their resurrection; for the simple membrane of several species bursts on evaporation of the water: the animal is dispersed, and reduced to an unconnected and disordered heap of fragments. “The arm-polypus is no less - simple simple than the animalcula of infusions, being composed but of a granulated gelatinous skin. If simplicity of structure influenced the resurrection of animals, the arm-polypus would certainly be one ; and it seems so much the better adapted for resurrection, as it continues alive notyithstanding every method has been taken to destroy animation. It is demonstrated that these polypi sustain no injury by , being turned , several times outside in, like a glove, or by being cut asunder. If the head is cut off, a sort of hydra with many heads arises, each of which receives food by a different mouth. If these new heads are cut off, new hydras spring up, and each head creates a polypus fit for the formation of more hydras: in short, every particle, even the smallest fragment of a polypus, unfolds, .# becomes a new polypus. If an animal so mangled and lacerated does not die, will it not be very credible that, only being allowed to remain dry, it may still retain the faculty of resurrection? But facts prove the reverse. The arm-polypus always dies when the water evaporates; and this happens equally whether it is immediately exposed to the air, or lies concealed among its native sub-aquatic herbs. hen the water is almost exhausted, the arms

are retracted into the animal; it.

contracts within itself, and dies. It never recovers, though water is copiously supplied. I speak of the arm-polypus, for it is the only species I have been able to find, and is the smallest of Trembley’s arm-polypi. “Next to polypi and infusion animalcula, according to my description, the organization of the 1803.

sloth seems to be the most simple. We may say the same of the anguillae of tiles and blighted corn, two species of * which may properly be classed with so great a number of the inhabitants of fluids from their organization. Under the tremella in water are often found minute eels, very like those of tiles in size, shape, and simplicity of organization. I have frequently had the curiosity to let them dry, by the water evaporating: all endeavoured to conceal themselves where the filaments of the tremella were thickest ; and when evaporation was complete, they perished, remaining -partly entwined among the filaments, and partly heaped above one another. If immediately wet, they revive; but never, if a few minutes elapse.

“The eels of vinegar give the strongest evidence of vigour : though they continue motionless when the fluid fails, and are apparently dead, they recover life and action, if wet, after a quarter of an hour. Sometimes I have succeeded in reviving them after half an hour. I do not call this resurrection: if it was such, I cannot see why it should not succeed anew when wet with vinegar, in even a longer time: we may rather say,

they do not die so soon as the eels

of the tremella, and many other insects left dry : life, though suspended, is preserved, and ap

pears on humectation. “I can discover no greater simplicity in the tremella and nostoc than in many plants that do not revive. Let us throw a hasty glance on the truffle. What yegetable is more simple 2 No roots, tendrils, or fibres, internal or external ; a substance equally compact and uniform throughout, O only

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experiments demonstrate that the

vital principle of animals with a heart originally resides in the irritability of this muscle. His experiments are too well known to need repetition. In animals which have no heart, it is more than probable that the principle of life resides in the irritability of their muscles. This being admitted, if the state of the animals is such that the irritable nature of the heart and muscles is destroyed, so as to leave no hope of reparation, it is clear that the animal not only dies, but must always remain dead : if the irritability is such that it may be re-exeited, either naturally or by art, it is indubitable that the animal will pass from death to life. It will not signify though it remains dead a long time, even for an age. The reader comprehends my idea. When wheel animals, sloths, and the eels of tiles are deprived of water, their irritability is evidently lost, and they die. Other animals, having once lost this irritability, never recover it; but it is awakened in wheel animals, sloths, and eels,

and they return to their origin: life by humectation. “From the same principle, may we explain why, in certain cases, these animals lose the resurgent property when exposed to powerful heat or penetrating odours, or when some liquids and electricity act upon them. Such agents injure the muscular structure, as appears by the rupture of the body and destruction of the irritable power residing in it. This perhaps is the reason why frequent humectations prejudice resuscitant animals; for I have really seen it; and in particular observed, that the members of the eels of blighted corm were injured and lacerated by repeated humectation. “We must conclude, from the whole, that as irritability resides in the glutinous part of the muscle, this part of resurgent animals has qualities very different from the irritable parts of other animals, though we are profoundly ignorant of what constitutes the #. because we are profoundly ignorant of what the gluten consists. “I wish to be sincere. A conclusion against the hypothesis may be deduced from my experiments. Irritability is recognised by its appearance, that is, on touching the muscular fibre with any stimulant. it contracts, and becomes rigid. I have often stimulated the muscular substance of the eels of blighted corn and tiles, with an extremely fine iron point, and attentively observed the consequence. The muscular fibre always see to contract a little, when touched, but I must acknowledge the same thing happened to the anguillz of vinegar, and to other analogous animalcula, which do not o: e

the privilege of resurrection. There are even some aquatic and terrestrial vermiculi more irritable than the eels, since, with the most gentle touch, they contract and swell, until they become many times as thick and short. The objection is therefore confined to this : there are some animalcula which do not revive, though as irritable, even more so than those that do. But it does not affect my hypothesis, for the principle of resurrection is not placed in the greatest and most perfect irritability, but in an irri. tability which, after cessation, may be renewed by means of certain circumstances, though it otherwise appears to be less active than in other animals. “If this hypothesis does not seem fully lo. to plants, in what concerns their irritability,

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MAGNet 1s M of the EARTH.

r {From Dr. You Ng's ANALYsis of the PRINciples of NATURAL Philosophy.]

“ 61. HE earth has been supposed to be a great magnet. “. For it produces all the phenomena of a natural magnet. “The learned Mr. Kirwan has, with great ingenuity, endeavoured to show that the earth is a great magnet, formed by the chrystallisation of its iron and magnetic ores, from a fluid state, in which it existed at its formation. And as the shoots of the chrystals would be found in that direction in which they were least disturbed, they would all lie orderly in a direction parallel to the axis of the

earth, and the axis of the magnet coincide with the axis of rota

tion. “Nevertheless, there appear trong objections to this hypothesis—See AEpinus, p. 300. s, 1. Iron is not found to be heavier near the poles, than towards the equator. 2. If a bar of soft iron be held vertical, it is rendered magnetic ; if horizontal, it quickly loses that power: therefore in the vertical position it ought to be heavier than in the horizontal, which does not appear to be the case— See Cavallo, p. 93. 3. If a magnetic needle, lying on a piece of O 2 cork, cork, be floated on water, it ought always to move to the northern side of the vessel, and not continue at rest in the middle, 4. Though many stones and ores are impregnated with iron, yet they are not in that state magnetical—See Cavallo, p. 16; that is, they will not affect a magnetic needle, though they themselves may be affected by a magnet. 5. The magnetism of the earth seems incompatible with the variation of the needle.

“.62. The poles of any magnet will be directed one towards one of the magnetical poles of the earth, the other towards the other.

“This follows from art. 7 and 61. The pole which is directed towards the north pole of the world, is called the north pole of the magnet; the other the south pole.

“.63. The magnetic axis of the earth is not coincident with the axis of revolution.

“For the north pole of the magnet is not directed exactly towards the pole of the world. This is called the variation.

“64. The magnetic needle is subject to a i. Innoving in northern latitudes, generally towards the west before noon, and afterwards gradually returning. “It has been conjectured that this may arise from the diurnal change in the heat of the earth; for the eastern parts of the earth being heated faster in the morning than the western, their attractive force on the needle will be weakened, by art. 18, and therefore the needle will move westward. “But the magnetical nucleus, to which we attribute the direction of the magnetic needle, is

certainly buried at a very considerable depth below the surface of the earth; whereas we know that the line which separates the terrestrial crust, subject to the influence of heat and cold, from that which is not subject to it, does not lie far below the surface; for in caves of even moderate depth, the thermometer preserves a permanent state.

“ 65. The magnetic needle is subject to an annual variation.

“Dr. Halley endeavoured to account for this phenomenon, by supposing that the axis of the magnetic nucleus was not exactly coincident with the axis of the earth, and that this nucleus was also moveable within the body of the earth. However, it has been found that the variation is not re

ular in any place, as it ought to i. on this hypothesis. It is however singular, that the artites, or eagle stone, which is of the class of iron ores, contains a nucleus, which is frequently moveable in the centre of the stone. See Fourcroy's Chem. v. iii. p. 219.

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