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would be himself again- for minds do not grow old or wear out, except by the effects of the body on them.
But to be serious. When alone, I am not above fiveand-twenty. I can entertain myself with a succession of inventions, which would be more effective if they were fewer ; I forget that I am sixty-eight, and if, by chance, I see myself in the glass looking very abominable—I do not care.
• What is the moral of this ?– That, as far as my poor experience goes—and 'tis said that we must all be fools or physicians at forty-occupation is the best nostrum in the great laboratory of human life for pains, cares, mortifications, and ennui : it amuses in sickness, it lightens the distress of circumstances, it acts as a gentle opiate to ill-requited love, it is a solace to the heart when a fellow-creature can be benefited by our exertions, and even in sorrow—even when the heart is sinking under the load of grief—if we can feel it a duty to bear up, we find it an Atlas to the human mind, giving it strength to support what might otherwise crush it.
• But to treasure up the power of occupying ourselves in a manner to interest us in old age, we must begin, my dear young friends, by occupying ourselves in youth, by cultivating some talent, some taste to which our mind leads us, which may amuse our solitary hours as we advance in life-and, if it has a useful tendency, so much the better-never should the day pass in which a young person ought not to endeavour to make some step forward to improvement; if we do so in youth, the taste will not depart from us in old age, and, instead of giving up the point of happiness, if we make it our aim to keep our minds awake to a sense of our duties, it will serve us in good stead, although Providence may not have gifted us with imagination or ingenuity. The independence of having your amusements within yourselves, my dear friends, will render you beloved and looked up to; the same independence in old age will prevent your ever feeling yourselves a burden on society. Rich in your own resources, you will ask no subscriptions from others, but
gladly afford a share of what little it may be in your power to bestow.' With this delightful picture of happy old age,
I niust close my · Pilgrimage to Balcarres, from which I only hope the reader may derive one-tenth of the pleasure which it was the means of giving to myself.
REGENERATION OF PARTS IN ANIMALS.
THERE is a power in nature for replacing or reproducing parts which have been injured or lost. It is least conspicuous in the higher animals, and increases as we descend to the lowest. Even in man, however, it exists to a considerable extent. When a bone in our bodies is broken, and the parts separated so as to leave an interval less than an inch, the two broken ends will throw out matter, and fill up the space with new bone. In the case of a dislocation, which is allowed to remain unreduced, a new joint is usually formed, in all respects resembling that put out of use. Even when a whole bone has been destroyed by disease, nature generally contrives to make a new one in its place. The new bony matter is thrown out, sometimes within, and sometimes around the dead shaft; and when the latter has been removed, the new structure gradually assumes the regular form, and all the attachments of muscles, ligaments, &c, become as complete as before. This power of nature is most apt to be shewn in young persons; and it appears that some individuals have
it in a much greater degree than others. A very curious example is recorded by Mr White in his work on the Regeneration of Animal and Vegetable Substances, 1785. A child, born a few years ago to a lady of rank, had two thumbs upon one hand, or rather a thumb double from the first joint, the outer one less than the other, each having a perfect nail. When he was about three years old, I was desired to take off the
lesser one, which I did ; but to my great astonishment, it grew again, and along with it the nail. The family afterwards went to reside in London, where his father shewed it to Mr William Bromfield, surgeon to the queen's household, who said he supposed Mr White, being afraid of damaging the joint, had not taken it wholly out; but he would dissect it entirely, and then it would not return. He accordingly executed the plan he had described with great dexterity, and turned the ball fairly out of the socket; notwithstanding this, it grew again, and a fresh nail was formed, and the thumb remained in this state.'
In fishes this reproductive power is chiefly shewn in the fins, which are sometimes replaced after being lost by accident or disease. The teeth of sharks and other fishes are also renewed with the utmost facility when broken off. The power is more energetic in reptiles, and especially in the order to which the frog and toad belong (batrachia). In the salamander, for example, new legs with perfect bones, nerves, muscles, &c., are reproduced after the loss or severe injury of the original ones; and in the Triton, a perfect eye has been formed, to replace one which has been removed. In the true lizards, the tail, when lost, appears to be restored; the new part contains no perfect vertebræ, however, but merely a cartilaginous column, like that of the lowest fishes.
In the articulata, the regenerative power is very considerable. The spider and other arachnida (including the scorpion) may lose their legs with impunity, for new ones will grow to replace the old. So it is also with their brethren the crustacea. When the crab, lobster, or crayfish happens to have a limb or claw lopped off, a new one grows in its place. They frequently meet with such losses in the course of the strange operation of throwing off their shell, which they do periodically; and when such an accident takes place, kind nature never fails to repair it. The second articulation from the body is the part at which the fracture most frequently occurs, and is probably the only one from which the new growth will issue ; for, if the claw be broken off below that joint, the animal itself effects the removal of the upper portion, either simply casting it off by violent muscular contraction, or striking it against some hard body. Amputation of a limb seems to be a matter of the utmost indifference to this order of animals. It has often been observed in the Zoological Gardens, that when any person took hold of one of the land-crabs by a leg, the creature instantly threw off the limb in order to get free, and quietly
The larvæ of many of the insects can reproduce a missing feeler or leg, when the perfect insect cannot. Among the lowest of the articulated division-for example, in the annelides or worms—segments of the body become complete animals ; but in the highest of this class, the phenomenon only takes place in the segment which contains the head. The head of the snail has been known to be replaced after being cut off, provided an organ of particular consequence (the cephalic ganglion) is uninjured ; but for this regeneration a constantly elevated temperature is said to be necessary.
When we arrive at the lowest department of the animal kingdom, we find this reproductive power in its greatest activity, insomuch that in some tribes (polypifera, asteria, &c.) any portion cut off becomes an entire animal. A single leg of the star-fish reproduces all the rest, and the minutest cuttings of the hydra acquire an independent existence. At the very extremity of the chain, there are creatures which regularly multiply by detaching portions of themselves, these detached portions being equivalent to a new generation. This, according to modern physiologists, is the simplest of all the modes of multiplication. We meet,' says Dr Roget, with frequent examples of this process of fissiparous generation, as it is termed, among the infusory animalcules. Many species of monads, for instance, which are naturally of a globular shape, exhibit at a certain period of their development a slight circular groove round the middle of their bodies, which by degrees becoming deeper, changes their form to that of an hour-glass ; and the middle part becoming still more contracted, they present the appearance of two balls, united by a mere point. The monads in this state are seen swimming irregularly in the fluid, as if animated by two different volitions ; and, apparently for the purpose of tearing asunder the last connecting fibres, darting through the thickest of the crowd of surrounding animalcules ; and the moment this slender ligament is broken, each is seen moving away from the other, and beginning its independent existence. Each animalcule, thus formed by the subdivision of its predecessor, soon grows to the size which again determines a further spontaneous subdivision into two other animalcules; these, in course of time, themselves undergo the same process, and so on to an indefinite extent. The most singular circumstance attending this mode of multiplication is, that it is impossible to pronounce which of the new individuals thus formed out of a single one should be regarded as the parent, and which as the offspring, for they are both of equal size. Unless, therefore, we consider the separation of the parts of the parent animal to constitute the close of its individual existence, we must recognise an unbroken continuity in the vitality of the animal, thus transmitted in perpetuity from the original stem, throughout all succeeding generations.
It is in the animal kingdom only that we meet with instances of this spontaneous division of an organic being into parts, where each reproduces an individual of the same species. All plants, however, are capable of being multiplied by artificial divisions of this kind : thus a tree may be divided longitudinally into a great number of portions, or slips, as they are called ; any one of which, if planted separately, and supplied with nourishment, may continue to grow, and may in time, reproduce a tree similar in all respects to the one from which it had originated. This inherent power of reproduction exists even in smaller fragments of a plant; for, when all circumstances are favourable, a stem will shoot from the upper