general view of its present state and probable advancement in future, noticing some of the objects of supplementary improvement, with hints for compassing them. It only remains to conclude with a brief summary of how far the art of horticulture has benefited mankind, in past and at the present time, and how far it contributes to both public and private happiness. The general face and aspect of the country is enlivened and enriched by the efforts of gardening. From it the palace receives its highest exterior embellishment, the saloons and chambers thereof are perfumed by its sweets, the arcades and corridors ornamented by its blossoms. Gardening provides the most exhilarating and salubrious luxuries of the banquet; the tables are garnished by its products, and the fruiteries and confectionaries, as well as the green larders, are supplied. No less is the humble cottage cheered and adorned, when its ivied porch and vine-clad gable exhibit marks of horticultural industry; and this extended into the well-stocked garden, yields many a wholesome addition to the homely fare of the frugal cottager. For other ranks of society the markets are supplied with a superabundance of the sweets, the delicacies, and wholesome esculents from the garden, forming half the food of man. The loom is furnished with much of its filacious substances, the ship and house builder with their indispensable material; the laboratory is supplied with the chief part of the various qualities from which are drawn or compounded the medicines for human ills; and much of the dyers' colours and artists' tints are obtained from the same productive source. By the assistance of horticulture our colonies have become the most valuable portions of the face of the earth. By the master mind of a Sloane and others, the art was employed to transport from their native place to the isles and continent of the western world, "the sweet cane," the coffee, fruits and spices, as well as drugs and dyes of the east; and the oriental world is now enjoying many of the natural products of the west*. Thus horticulture, as the handmaid of civilization, has mainly contributed to promote the interests, administer to the comfort, and provide for the principal wants of all mankind. J. M. Tea is not mentioned, because it has not been an object of cultivation in the western world. De l'Influence des Agens Physiques sur la Vie. Par [Continued and Concluded.] OUR analysis of Dr. Edwards's treatise terminated in the last number but one with the influence of respiration over the production of heat in vertebrated animals. The remaining chapters are devoted to experiments illustrating the phenomena of transpiration, absorption, temperature, light, &c., with applications to the human system. It is impossible to allude to transpiration without immediately conjuring up in imagination the figure of old Sanctorius and his balance, the honest physician accurately weighing himself, so as to calculate his losses by transpiration at different periods, and compared with the quantities of food which he swallowed. But, in his days, the knowledge of physics was at a very low ebb, and hence his aphorisms require the more finished touch of modern physiology. It appears, that in twenty-four hours the losses which the body sustains in weight are not equal throughout the day and night, but exhibit fluctuations, depending on various circumstances referrible to physical and vital causes. Among the first may be reckoned temperature and pressure, dryness and humidity, repose or agitation of the air; and among the second are, the constitutional health, repose and activity of the body, &c., while some of the physical causes possess a double influence, both vital and physical, such as light. Under such circumstances it is clear, that knowledge of physical laws is essential, in order to compute the individual influence of physical agents in retarding or accelerating tran spiration. The importance also of this function in the animal economy enhances the value of an intimate acquaintance with its vital relations. The influence of food upon transpiration is the first object of inquiry. Sanctorius declares this function to be feeblest during the first three hours after a meal. But Dr. Edwards agrees with others in denying the direct tendency of stomachal digestion to retard transpiration. The presence of food in the digestive canal attracts thither, it is true, a flow of liquids from the surface of the body, and thus creates a temporary diminution of transpiration. Sleep seems to possess a direct influence over transpiration in increasing its quantity, as is seen in children at different ages, whose bodies are bedewed with fluid under circum stances when neither the temperature of the air, nor their covering, can explain the phenomenon. Under certain limitations of temperature, the passage of fluid from the surface of the body is accelerated or retarded as the air is more or less saturated with moisture. When the air did not exceed 20° Reaumur in its temperature, Dr. Edwards found a moderate dryness renders the losses of weight by transpiration six or seven times greater than in cases of extreme moisture. The union of vital and physical causes tends to make the phenomena in these experiments appear complex in their conclusions, and render calculations liable to error. If the air be dry, the waste by transpiration, compared with that of moist air, exceeds, on account of the evaporation of water being most abundant in a dry atmosphere. And this occurs equally in the dead and living body as a physical law. But, in the living state, the increase of transpiration will vary from causes within, which modify those acting without the system. When the air is agitated, the temperature of strata of air in contact with the body is affected, and so also is the degree of moisture. If the warm and moist air close to the body be replaced with a cooler air, evaporation is indefinitely increased. The slightest and most imperceptible agitation in the air produces its effect upon transpiration. The pressure of the atmosphere becoming lessened, the evaporation of liquids is a necessary physical result. In order to ascertain if this took place also in the living body, Dr. Edwards placed one animal under a bell-glass, from which part of the contained air was removed, while another was exposed to the pressure of the air without. The result was, that the animal in the rarefied air lost more weight than the one under ordinary pressure. Besides the cutaneous transpiration, vapour is constantly exhaling from the lungs, as may be seen by breathing on a mirror, or into a glass vessel. Sanctorius and others knew of this; but their deductions from experiments on the relative quantities are incorrect. Lavoisier and Seguin arrived at better conclusions; for chemistry and physics in general were more understood in their time. These authors estimate the mean daily loss by the lungs and the skin at two pounds thirteen ounces, of which one pound fourteen ounces go off by the skin, and fifteen ounces by the lungs. The loss thus sustained is derived partly from the pulmonic water evaporated, and partly from chemical changes effected by respira tion. Though we cannot precisely measure the proportions of the two losses, the former is evidently the preponderating means of dissipating the body's weight through the lungs. It appears that, whether it be from the skin or the lungs, all aqueous discharge is by evaporation, and the expenditure from the surface of the body far exceeds what happens to arise from the lungs, at least in man, whose structure would lead to such a conclusion. In the lungs the transpiration is most constant, and it fluctuates very much from the skin. The phenomena of absorption in moist air and in water, are next subjected to experimental examination, which tends to show, that the preponderance of absorption over transpiration, does not solely depend on temperature, but on the greater or less degree of fullness of the vessels. The less the body is saturated the greater will be the absorption; so that if it suffers considerable previous loss by transpiration from evaporation without subsequent replenishment, it is placed in one of those conditions most favourable for the increase of absorption. In the chapter following this portion of the work, and which treats of temperature, the curious and interesting experiments of Delaroche and Berger are alluded to. Several species of vertebrated animals were placed by these authors in a temperature varying from 42° 5' to 45° cent., when most of them remained quiet at first, but after the lapse of half an hour they became restless, and in three quarters of an hour their respiration was hurried on to almost suffocation. The result showed, that vertebrated animals in a dry air, heated to 45° cent., are near the utmost limit of temperature in which they can exist a long time; for, after recovering the effects of this heat, they were removed to an atmosphere of from 56° 25' cent. to 65° cent., when, excepting one frog, they all died, and at different periods between the space of twenty-four minutes, and one hour and fifty-five. We know not of human beings supporting so great a heat during so long a time; but during a short period a higher temperature has been supported. A young man remained twenty minutes in an oven, heated to 210° Fahrenheit, without much inconvenience, when his pulse was raised from twenty-five to an hundred and sixty-four, which is the highest degree of rapidity; the temperature was nearly that of boiling water. However, M. Berger and Sir Charles Blagden exceeded this, the former enduring 109° 48 cent. during seven minutes, and the latter from 240° to 260° Fahrenheit eight minutes. - M. Delaroche could not remain more than ten minutes and a half in a vapour bath at 37° 5 cent., increased in eight minutes to 51° 25′ cent., and subsequently lowered one degree. M. Berger was obliged to get out of a vapour bath at a temperature between 41° 25' to 53° 75', in twelve minutes and a half. He was much weakened, tottered on his limbs, and was affected with giddiness; and these symptoms continued some time. Yet both these persons sustained equal and superior temperatures in dry air during a much longer time, and without any remarkable inconvenience. The sensation in damp air is more intense, and resembles that of contact with boiling water. It is said, that the peasantry of Finland can remain upwards of half an hour in a vapour bath heated to 70° or 75° cent. It is evident, that a bath of hot water, at the same heat, will produce a much more powerful influence upon the animal economy. M. Delaroche sought to ascertain what increase the temperature of the body acquires under certain degrees of heat. In a vapour bath, heated from 37° 5' to 48° 75' cent., the temperature of the body was raised by 3° 12′ cent., as indieated in the mouth. Ŏn M. Berger making the same trial with vapour at from 40° to 41° 25', the temperature of his body acquired 1° 87' in fifteen minutes. But this object is better achieved by experiments on animals of warm blood than on man. Accordingly, different species of mammiferæ were placed in an oven heated to 93° 75' cent. Notwith standing the variety of species, birds, &c. inclosed in dry air, heated as stated above, all of them acquired nearly the same increase of temperature; we may, therefore, fairly infer, from results so uniform, that man and warm-blooded animals, under the influence of excessive heat in dry air, cannot, during life, sustain an elevation of vital temperature beyond 7° or 8° cent. In the cases of the animals last-mentioned, they all died. These results are not applicable in like manner to cold-blooded animals; 40° 93' cent. is the greatest degree of heat which these were found to reach at the period of their death. The last physical agent which our author notices, is that of light, and its influence is considered in a two-fold point of view, physically and vitally; for such is its effect upon animal bodies in their living state. This chapter is equally interesting to the pathologist and the natural philosopher. Light will be found, in practice, to be among the curative means of many disorders. The uncovered parts of the human body receive the action of luminous matter, which is |