have limits set to its duration, beyond which it fails to 'rences of early life continually suggest themselves, a d keep in healthy motion the animal faculties. The ap- are minutely called to remembrance. paratus of life is evidently destined but to last for a certain time. Old age creeps on apace, and the vital flame burns fainter and fainter, till at last it sinks in the socket, and is seen no more. The commencement of decay is perceptible even in youth itself. The child at first grows quickly, from the soft and yielding state of all its vessels; but gradually these begin to thicken and get harder-a greater proportion of earthy matter is adding to the bones. The extremities grow large, while the heart itself does not increase in an equal degree; hence the circulation becomes less and less quick, till the period of full growth. When the growth of the body can proceed no farther, a degree of fatness not unfrequently occurs. This proceeds from the superabundant nourishment produced from the food, which, from the impetus or force of the circulation being more lessened by the greater extension and resistance of the body, accumulates in the cellular textures and by the sides of the extreme vessels. In every part of the body, the induration produced by approaching age becomes conspicuous-in the bones now wholly brittle, in the skin, in the tendons, in the glands, in the arteries, and in the brain itself, which gets firmer and drier. Moreover, the arteries continue to get denser, narrower, and even shut up in their minute branches. At the same time, the nerves become more and more callous and insensible to the impressions of the senses, and the muscles to irritation; thus, the contractile force of the heart, and the frequency of its pulsations, are diminished, and, of consequence, every force which impels the blood into the ultimate vessels. The quantity of humours is diminished in the denser body; the moisture which lubricates the solid parts everywhere manifestly decreases. Nor is the quantity of humours only diminished; they themselves likewise become vitiated. They were mild and bland in children; they are now acrid, salt, and fetid, and loaded with a great quantity of earthy matter. This circumstance of the superabundance of earthy matter is evident in the gouty concretions in the joints of old people, in the frequency of stone, and in the arterial tubes, and even the heart itself, being frequently converted into real bone. The rigidity of the whole body, the decrease of the muscular powers, and the diminution of the juices, constitute old age, which sooner or later comes upon all men-sooner, if subjected to violent labour, or addicted to pleasure, or fed upon a too scanty or unwholesome diet; but more slowly, if they have lived quietly and temperately, or if they have removed from a cold to a moderately warm climate. There are three obvious divisions of human life-a period of youth, including the period before the age of 30; of maturity, from 30 to 50; and of old age, commencing about the period of 50 or 60. David speaks of the age of man being, in his time, only threescore years and ten, or in rare cases fourscore years, which may be reckoned the average limit of human existence. After the period of 50 or 60 years, varying of course in different constitutions, the marks of old age begin to make their appearance. The skin becomes more lean and shrivelled; the hair changes to a gray colour, or baldness occurs; the teeth drop out, and, in consequence of this, the lower parts of the face, about the mouth and jaws, incline inwards; the muscular motions of the body become less free and elastic-this is especially seen in walking, old people generally treading on the whole base of the feet, and hence have a shuffling gait; the blood circulates slowly; the animal heat is diminished; the pulse occasionally intermits, and the whole energies of the animal frame become lessened; the eyesight begins to fail, and dulness gradually comes over all the senses; the memory undergoes a remarkable change—while recent events pass through the mind and make no impression, the occur

Although usually seventy years is the extreme period of human life, yet a small proportion of those born ever reach even this; a few rare instances occur where one hundred years or upwards are attained. The famous Parr lived to the age of 159 years; he married at the age of 120, and, when 130, was able to thrash, and to do every description of farmers' work. He was at last brought from the pure air and the homely diet of the country, into the family of the Earl of Arundel, in London, where he drank wine and lived luxuriously. The sudden change of diet and circumstances, however, proved quickly fatal to him. Henry Jenkins, another poor man, lived to the astonishing age of 169 years, and retained his faculties entire. Some time ago, a statement appeared of the ages of the resident pensioners of Greenwich Hospital, which contained at the time 2410 inmates. Of this number, 96 had attained to or passed the age of 80; one only was above 100; 15 were 90 or more; and 80 were 80 or upwards. About 42 of the 96 were of aged families, and in some of this number both parents had been aged. Longevity has in a great number of cases been found to be hereditary. Eighty of the 96 had been married; 79 were in the habit of using tobacco in some form or other, and 48 had drunk freely; 20 were entirely without teeth; 52 had bad, and 14 good teeth. But the oldest man in the house, who was 102, had four new front teeth within the five preceding years. The sight was impaired in about one half, and hearing only in about a fifth part of the number. Old people are not generally inclined for much exercise, nor is it suited to their stiff joints and impaired vigour; for the same reason they cannot endure much cold. Cheerful company, especially the company of the young, is peculiarly grateful to old people. Innocent amusements and recreations are also of great consequence, and the mind should be exercised in some useful or amusing pursuit. Cities, or at all events constant and agreeable society, are favourable to the condition of old age. lonely, secluded country places, the mind sinks prematurely into a total gloom and blank, for want of sufficient stimulus and variety to keep up the vigour of thought and play of ideas. Few deaths occur from what is commonly called old age, or a gradual and simultaneous decay of all the functions. It may be said to happen when the powers gradually decay, first of the voluntary muscles, then of the vital muscles, and, lastly, of the heart itself; so that, in an advanced age, life ceases through mere weakness rather than through the oppression of any disease. The heart becomes unable to propel the blood to the extreme parts of the body; the pulse and heat desert the feet and hands, yet the blood continues to be sent from the heart into those arteries nearest to it, and to be carried back from them. Most commonly, however, some one part gives way, and disease gradually coming on, cuts off the lingering flame of existence. Thus the body, after having grown up to maturity, and flourished in its prime, sinks to the earth, and moulders into the elements of which its several parts are composed.

CONCLUSION.

In

The admirable structure of the body of the human being-its superiority in every respect to that of the lower animals-afford a most perfect proof of design in the all-wise Creator, and is one of the most striking instances of the impossibility of our formation being the result of blind chance. Paley, after going over a great number of examples of this kind of design in a Creator, proceeds to state that, in all "instances wherein the mind feels itself in danger of being confounded by va riety, it is sure to rest upon a few strong points, or per

haps upon a single instance. Among a multitude of | strictly mechanical; nor have I read or heard of any proofs, it is one that does the business. If we observe solution of these appearances, which in the smallest in any argument (he continues), that hardly two minds degree shakes the conclusion that we build upon them. fix upon the same instance, the diversity of choice shows The works of nature require only to be contemplated. the strength of the argument, because it shows the num- When contemplated, they must ever astonish by their ber and competition of the examples. There is no sub-greatness; for, of the vast scale of operation through jeet in which the tendency to dwell upon select or single topics is so usual, because there is no subject of which, in its full extent, the latitude is so great, as that of natural history applied to the proof of an intelligent Creator. Perhaps the most remarkable instances of mechanism in the human frame are-the pivot upon which the head turns, the ligament within the socket of the hip-joint, the pulley or trochlear muscles of the eye, the epiglottis, the bandages which tie down the tendons of the wrist and instep, the slit or perforated muscles at the hands and feet, the knitting of the intestines to the mesentery, the course of the chyle into the blood, and the constitution of the sexes as extended throughout the whole of the animal creation. To these instances, the reader's memory will go back, as they are severally set forth in their places; there is not one of the number which I de no think decisive; not one which is not | One Being has been concerned in all."

which our discoveries carry us, at one end we see an intelligent Power arranging planetary systems, and, at the other, concerting and providing an appropriate mechanism for the clasping and reclasping of the filaments of the feather of the humming-bird. We have proof, not only of both these works proceeding from an intelligent agent, but of their proceeding from the same agent; for, in the first place, we can trace an identity of plan, a connection of system, from Saturn to our own globe; and, when arrived upon our globe, we can, in the second place, pursue the connection through all the organized, especially the animated, bodies which it supports. We can observe marks of a common relation, as well to one another as to the elements of which their habitation is composed. Therefore one mind hath planned, or at least hath prescribed, a general plan for all these productions.

VEGETABLE PHYSIOLOGY.-BOTANY.

Plants are in the main easily distinguishable from

animals, and the consideration of them falls under different sciences. Yet it is not easy to say where the animal world ends, and the vegetable world begins. The

two seem to melt into each other in the class of exist

ergy, or spontaneous locomotion. With respect to the that neither plants nor animals come into existence withpowers of reproduction, it must be carefully impressed, kinds of animals, as, for example, maggots, locusts, and out a parentage. It was at one time supposed that some myriads of smaller creatures, were produced from external causes alone, such as putridity, or a certain state of the atmosphere; but such notions have long been abandoned by men of science, and it is placed beyond the possibility of doubt that all animals and vegetables whatsoever, notwithstanding any mystery that may attach to their appearance, are the offspring of others of

their own type.

The method of reproduction, as will be afterwards ences called zoophytes, which appear a combination of shown, is different in different plants, but, as a general both plant and animal. We are not, however, to sup- principle, it may here be stated that the parent vegepose that the highest class of plants are thus connected table is charged with the function of liberating germs or with the lowest or simplest class of animals, and that the seeds, which vegetate as soon as brought into a condition organic world is consequently one continuous chain. fitted for their growth. A seed is like an egg in chaThe two systems may be rather said to be united at a point racter, for it possesses in itself that amount of nourishnear the base of both, above which they rise side by side. ment which will enable it to subsist in the ground during Apart from this connection, plants are to be distinguished germination, or until it draws the means of existence from animals by not only certain external appearances, from the soil and atmosphere. Most kinds of seeds, but by the absence, in them, of what animals possess, an internal principle not easily described, but traceable in certain very remarkable results, namely, motion from place to place, a selection of advantageous circumstances, and a power of adapting means to ends.

being contained in husks or shells for their preservation,
are able to retain their vegetative power for a long
period of time, if entirely excluded from heat, air, and
moisture; thus, on turning up soil which had been co-
observed to arise from the long-buried seeds.
vered centuries ago, a new order of vegetation is always

It may be further mentioned, as a provision in the

Of the nature of life, or the vital principle, science does not profess to be able to give an explanation. In using the term, we only mean that power or quality economy of vegetation, that, while each species of plants resident in certain structures, by which they are enabled is incapable of being transformed by reproduction into to incorporate with themselves those nutritive particles of matter which they require, and to reproduce structures of their own species or type. The most simple forms of life are observable in plants whose economy is limited to mere absorption of nutrition and reproduction; and it is only when we reach the link that unites vegetables with animals, that we find any thing sensitive, a nervous en

See art ZOOLOGY

any other, it is possible, in some instances, as in the animal species, to produce a hybrid or mixed breed, and, with the additional means afforded by cultivation, plants and fruits may be improved in quality to a very high defields and hedges, is the uncultivated original of the difgree. Thus, the common sour crab, growing wild in our ferent varieties of the apple. Yet, to sustain this im provement, constant culture, transplanting, crossing, or grafting are required. The plant is only improved as

respects itself, and if its seeds be allowed to grow up without culture in a poor soil, they will produce plants exactly resembling their humble original.

The term of vegetable existence, from the period of germination till the final decay of the plant, is extremely various: some plants are annuals, or grow but for one year or season; while others are perennial, and continue their growth from year to year; trees are among the longest lived plants, some being known to exist for upwards of two thousand years. The reproductive powers of plants are likewise very varied; but it may be stated, in general terms, that in each case nature has provided effectual means of perpetuation, either by means of roots or seeds, or by both. This power of reproduction is strikingly observable in such plants as the potato, which propagates by oviparous seeds pendant from the stalks, and by the tubers clinging to the roots in the ground. In most instances, the artificial deprivation of the seeds before they arrive at maturity, incites the reproductive powers of the roots, and they increase in bulk, or throw up new plants at a distance from the parent stem. When annuals have ripened their oviparous offspring (grain in the ear, for instance), the object of their growth is accomplished, and they forthwith droop and decay.

action which can affect vegetation there very much more at one time of the year than at another; and therefore, considered with reference to the sun alone, the vegetation there is not only generally ever-green. but ever growing, ever-flowering, and ever-ripe and in fruit.

In the extreme northern and southern latitudes, a por tion of one half of the year is continual day, and a cor responding portion of the other half continual night; and when the continual day approaches, if part of the heat of the sun were not occupied in melting snow and ice, and turning into vapour the water which clouds the atmosphere and mitigates the ardour of the solar heat, the action of the sun in those high latitudes would at these times be excessive. As it is, vegetation, during the short period that it acts, is more vigorous in such parts of the polar countries as are out of the range of the cold produced by melting snow or ice, than it is in any other part of the world; and even in Lapland, we have the expansion of the bud, the blowing of the flower, the ripening of the fruit, and the preparation of the new bud, in little more than half the time in which these operations take place in the temperate climates. This state of things requires a suitable character in the vege tables placed in those countries-they must be capable of resisting equally the ardour of summer and the rigour of winter. For this purpose, such vegetables as stand exposed to the air at both seasons, form complete buds, encased in a hybernaculum, composed of a number of scales of a resinous or gummy consistency, with thin strata of dry air between them; and buds so shielded are proof against the utmost severity of cold. The more lowly plants of such places are defended by the snow which covers the ground; and thus, though the action of the vegetable world is limited in its annual period, and also in the number of species in which it is dis

The development of vegetable life is greatly dependent on certain concurring agents, among which, in a particular manner, are included heat, air, moisture, light, and soil. Each of these agents, however, is limited to a certain range, and this range is different in different plants, so that excessive heat and excessive cold, and also the extremes of drought and humidity, are always unfavourable to vegetation generally, though not to all kinds of vegetables. Thus some mosses and other plants, whose parts are few and little developed, continue to grow in very cold weather, and even under the snow; | others which generally contain much juice in their sub-played, it is as perfect in its system, and as secure in its stance, but which are covered with an epidermis so compact that it resists the action of heat, and prevents any evaporation of the juice of the plant, live in situations where the heat is extreme, and during that part of the year when excessive drought renders the common vegetation as inactive as it is in polar countries during the depth of winter.

The condition of the atmosphere as respects temperature, moisture, and other qualities affecting vegetable life, is comprehended in the term climate. No two places at a distance from each other can be said to have the same climate, because each is subject to particular influences not affecting the other to the same degree. That district will possess the most genial climate, and be best adapted for the perfection of vegetable life, which at once lies most fair towards the sun, and is exposed to the action of refreshing rains, or is moistened in some other way. A free exposure to the sun throughout the year is equal to several degrees of latitude nearer the equator, other circumstances being favourable. The more free the exposure, the more readily will most plants blossom, and yield a rich fruit; so well is this understood in the grape countries on the Rhine, that the right bank of that river, which faces the sun, is reckoned to be much more valuable than the left, and commands a higher price for its wines.

The character of the vegetation in tropical and extreme northern and southern climates, is of the most opposite kind-the one luxuriant and continuous, and the other only for a short period during summer. In the tropical regions there is always about twelve hours of sunshine, and nearly the same length of darkness; and when the air is clear, the action of the sun is generally sufficient to occasion a suspension of the powers of many vegetables, or what is sometimes called a sleep of plants, during the heat of the day. But, unless for local circumstances, the chief of which are alternate successions of drough and rain, there is nothing in the mere solar

continuance, as in the tropical regions. Between these extremes, there is a regular gradation; and taking that and local observation along with us, we are in possession of at least the elements upon which a geography of piants may be formed.

While heat, variously modified, serves as prime exciting cause of vegetable life, air and moistare, or water, are elements in which the vegetables fod and exist. The soil in which the plants have their roots, and the atroosphere in which their branches and leaves flourish, are the great laboratories of nature, whence these elements are drawn. To understand properly how plants derive nourishment from these sources, it is necessary to ap peal to chemistry, or that branch of science which recog nizes the elementary properties of matter. The following are a few leading principles, briefly stated:

"The substances which constitute the principal mass of every vegetable are compounds of carbon with oxygen and hydrogen in the proper relative proportions to form water. Woody fibre, for example, is composed of such compounds of carbon with the elements of water. In another class of substances containing carbon as an element, oxygen and hydrogen are again present; but the proportion of oxygen is greater than would be required for producing water by union with the hydrogen. The numerous organic acids met with in plants belong, with few exceptions, to this class. A third class of vegetable compounds contain carbon and hydrogen, but no oxygen, or less of that element than would be required to convert all hydrogen into water. These may be regarded as compounds of carbon with the elements of water and an excess of hydrogen. Such are the volatile and fixed oils, wax, and the resins. The juice of all vegetables contains organic acids, generally combined with inorganic bases or metallic oxides; for these metallic oxides exist in every plant, and may be detected in its ashes.”*

Liebig's Organic Chemistry.

Nitrogen also forms a portion of most plants, being an | purposes of growth; and in proportion as the air is more important ingredient in the substance called gluten, or humid, it must perform this function less perfectly. We the starchy material of farinaceous vegetables. It is must therefore suppose that there is a certain degree of chiefly drawn in the form of ammonia from the soil to moisture, and of evaporative power jointly, in the air, which animal manures have been applied. In general, which is best adapted to the healthy action of plants, carbon is the fundamental and principal element in plants, but what this is must depend upon the nature of the and this is derived chiefly from the atmosphere. The plant, and must therefore be ascertained by direct obsercarbon exists in the atmosphere in the form of carbonic vation. Indeed, this is one of the circumstances which acid, or in a state of union with oxygen; and therefore, tends to the local distribution of the different kinds of nere appropriating the carbon, plants must necessarily plants, as we find them in a state of nature; but, like decompose the atmosphere. This process is actually the others, we cannot so separate it from co-operating performed by the vegetable kingdom. Plants possess the causes as to obtain the law of its action. There is one power of separating the carbon of the carbonic acid other circumstance connected with the air which is worfrom the oxygen, and, seizing upon the carbon, return thy of notice, and that is, whether it be more generally the oxygen to the atmosphere. stagnant or in motion. It is perfectly evident, that the action of stagnant air upon a plant must be every way less than that of moving air, whether we suppose the action to be of one kind or another; and therefore, up to a certain point, motion in the air must be favourable to the growth of vegetables. Of this there have been proofs by direct observation, in the same part of the world; and when we examine different parts of the world, we find proofs which are much more striking: thus, for instance, the trade wind of the Atlantic sets constantly against the shores of Brazil and Guinea, and up the valley of the Amazon, until its motion is gradually destroyed by the dense mass of vegetation over which it passes.

The process of decomposition and appropriation is performed by the leaves and other green parts of plants, these constituting the breathing apparatus. But, for the performance of this remarkable chemical action, aid from the sun's light is necessarily required. While vegetables are in a considerably darkened shade during the day, and in darkness during the night, carbonic acid is accumulated in all parts of their structure; and the assimilation of the carbon and the exhalation of oxygen commence from the instant that the rays of the sun strike them. As soon as a young plant breaks through the surface of the ground, it begins to acquire colour from the top downwards, and the true formation of woody tissue commences. Plants thus improve the air by the removal of carbonic acid, and by the renewal of oxygen, which is immediately applied to the use of man and animals.

The growth of plants, and their transformation of elementary properties in the soil and atmosphere, must hence be regarded as a protracted and various process in the chemistry of nature, proceeding on fundamental laws. In order that the process may not be defeated, pure atmospheric air, and also the sun's light, must be allowed in their proper proportions, independently of pure water. The air best adapted for robust vegetable growth is that of an ordinary density, near the sea's level. Generally speaking, the more elevated the station of the plant is, its action is the less, because the air is the less dense, therefore colder, and is understood to have greater evaporative power; but mountainous countries are generally much better supplied with humidity than plains; and therefore the dwarfed growth of plants in such situations must be considered as resulting much more from their diminished action than from any excess of evaporation. Hence, as we ascend the slopes of mountains which are of sufficient elevation for having their summits covered with perpetual snow, we find upon them plants resembling those of a succession of latitudes, gradually getting colder than the mean temperature of that which answers to the level of the sea, in the same latitude as the mountain. So that, upon very lofty mountains near the equator, the Andes in upper Peru, for example, we meet with something resembling the succession of plants in the whole quadrant, from the equator to the pole. But it is a resemblance only, and not an identity; because, although it be possible to find upon the side of such a mountain places which have the same mean temperature for the year as is found in every parallel of latitude, yet both the daily and the seasonal distribution of the sun's action are very different; and it necessarily follows that the nabits, and even the characters, of the vegetables are equally so.

Humid air supplies some vegetables with all the nourishment which, from their situations, they can possibly obtain; and therefore we may conclude that it is capable of affording ⚫ome nourishment to every vegetable. But the air also acts as a drain upon vegetables, in removing out of their structure a portion, and sometimes a very large portion, of that water which is necessary for the

The Oriental isles, and the southern part of the Malay peninsula, are in like manner exposed to a constant current of the air; and those two regions are, in respect of the number, the variety, the beauty, and the activity of their vegetable productions, the very gardens of the two hemispheres. Even when the current of air is an alternating one, the return of which is actually unfavourable to vegetation, such a situation is still highly favourable upon the whole. Of this we have striking examples in the valley of the Mississippi, the Malabar coast of India, and even in the British islands, and, generally speaking, along the whole of the west coast of Europe, where the advantage is not counteracted by some local cause.

Winds are therefore to be considered as performing an important part in the economy of nature. From northern and southern latitudes, where there is a small supply of sun's light during winter, with weak vegetation, and consequently a superabundance of carbonic acid in the atmosphere, the winds convey the deleterious material to tropical regions, where, by means of the brilliant sun's light and strong vegetation, it is readily and profitably consumed. Streams of wind in a contrary direction, or from the equator to the poles, in the same manner bring to us the superabundance of oxygen produced from tropical plants. While heat, moisture, air, and light, variously modified in the multifarious climates on the globe, produce the extraordinary diversity of vege table growth, another set of circumstances affect the life of plants, and these relate to the nature of the soil in which they are placed. Although properly belonging to GEOLOGY, we shall present a short exposition of what soils usually consist.

The soil is mainly composed of particles which have been disengaged by various means in the course of time from the rocks on which it rests. In some instances, and more particularly on hills, it is composed chiefly of pulverized materials from the rocks immediately at hand or beneath; but in many others, the pulverized matter has been washed down from high into low grounds, or transported by floods from great distances. The action of the air and water on rocks in dissolving them, and the power of the latter element in transporting the disengaged particles, are the principal causes of the present arrangement of the soil.

Notwithstanding the different appearances which the earthy covering of the globe exhibits, it is composed