were foon frozen, and appeared like a hoar-froft on the fides of the veffel, and on its whiskers; but while the vigour of life lafted, it dened the approach of the cold. However, from the hair being wet, and thereby rendered a good conductor of heat, there was a much greater confumption of it than in the former experiment. This haftened on a diminution of the power of producing it. The animal died, and foon became fliff; upon thawing it, we found it was dead.

IV. The fourth experiment was upon a toad. It was put into water just deep enough not to cover its mouth, and the whole was put into the cold mixture, now between 10° and 15°. It allowed the water to freeze clofe to it, which as it were clofed it in; but the animal did not die, and therefore was not frozen: however, it hardly ever recovered the ufe of its limbs.

I. I took a young growing bean, about three inches long in the talk, and put it into the leaden veffel with common water, and then immerfed the whole into the cold mixture. The water very foon froze all round it; however, the bean itself took up a longer time in freezing than the fame quantity of water would have done; yet it did freeze, and was afterwards thawed, and planted in the ground, but it foon withered. The fame experiment was made upon the bulbous roots of tulips, and with the fame fuccefs.

V. The fifth experiment was with a fnail, which froze very foon, in a cold between 10° and 13°; but this experiment was made in the winter, when the living powers of thofe animals are very weak: it might have refifted the cold more ftrongly in the fummer.

II. A young Scotch fir, which had two complete fhoots and a third growing, and which confequently was in its third year, was put into the cold mixture, which was between 15° and 17°. The last fhoot froze with great difficulty, which appeared to be owing in fome meafure to the repulfion between the plant and the water. When thawed, the young fhoot was found flaccid. It was planted; the first and fecond fhoot we found retained life, while the third, or growing fhoot, withered.

III. A young fhoot of growing oats with three leaves, had one of the leaves put into the cold mixture at 22°, and it foon was frozen, The roots were next put in, but did not freeze; and when put into the ground, the whole grew, excepting the leaf which had been frozen. The fame experiment was made upon the leaves and roots of a young bean, and attended with the fame fuccefs.

IV. A leaf taken from a growing bean was put into the cold mixture, and frozen, and afterwards thawed, which ferved as a standard.

ftandard. Another fresh leaf was taken and bent in the middle upon itself; a small fhallow leaden veffel was put upon the top of the cold mixture, and the two leaves put upon its bottom; but one half of each leaf was not allowed to touch the veffel by the bend; the cold mixture was between 17° and 15°, and the atmosphere at 22°. The furfaces of the two leaves which were in contact with the lead were foon frozen in both; but thofe furfaces which rofe at right angles, and were therefore only in contact with the cold atmosphere, did not freeze in equal times; the one that had gone through this procefs before, froze much fooner than the fresh one. The above experiment was repeated when the cold mixture was at 25°, 24°, and the atmofphere nearly the fame, and with the fame fuccefs; only the leaves were longer in freezing, efpecially the fresh leaf.

V. The vegetable juices above mentioned being frozen in the leaden veffel, the cold mixture at 280, and the atmosphere the fame, a growing fir-fhoot was laid upon the furface, alfo a bean leaf; and upon remaining there fome minutes, they were found to have thawed the surface on which they lay. This I thought might arife from the greater warmth of thefe fubftances at the time of application; but by moving the fir-fhoot to another part, we had the fame effect produced.

VI. A fresh leaf of a bean was exactly weighed; it was then put into the cold atmosphere and frozen. In this state it was put back into the fame fcale, and allowed to thaw. No alteration in the weight was produced.

It appears from the above experiments, that an animal must be deprived of life before it can be frozen. Secondly, that there is an exertion, or an expence of animal powers, in doing this, in proportion to the neceflity; and that the whole animal life may be exhausted in this way. Thirdly, that this power is in proportion to the perfection of the animal, the natural heat proper to each species, and to each age. It may alfo perhaps depend, in fome degree, on other circumftances not hitherto obferved: for from experiment II. and III. upon dormice, I found that in these animals, which are of a conftitution to retain nearly the fame heat in all temperatures of the air, it required the greatest cold I could produce to overcome this power; while in experiment IV. and V. this power in the toad and snail, whofe natural heat is not always the fame, but is altered very materially according to the external heat or cold, was exhaufted in a degree of cold not exceeding 10° or 150: and the fnail being the most imperfect of the two, its powers of generating heat were by much the weakeft.

That the imperfect animals will allow of a confiderable variation in their temperature of heat and cold, is proved by the following experiments. The thermometer being at 45°, having introduced the ball by the mouth into the ftomach of a frog, which had been exposed to the fame cold, it rofe to 49°. I then put the frog into an atmofphere made warm by heated water, and allowed it to ftay there twenty minutes; when, upon in troducing the thermometer into the stomach, it raised the quick

Glver to 64°. But to what degree the more imperfect animals are capable of being rendered hotter and colder, at one time than another, I have not been able to determine. The torpidity of thefe animals in our winter is probably owing to the great change wrought in their temperature by the external heat and cold. The cold in their bodies is carried to fuch a degree, as in great measure to put a ftop, while it lafts, to the vital functions. In warmer climates no fuch effect is produced. In this respect they refemble vegetables.

From the foregoing experiments it appears; first, that plants when in a ftate of actual vegetation, or even in such a state as to be capable of vegetating under certain circumftances, must be deprived of their principle of vegetation before they can be frozen. Secondly, vegetables have a power within themselves of producing or generating heat; but not always in proportion to the diminution of heat by application of cold, fo as to retain at all times an uniform degree of heat; for the internal temperature of vegetables is fufceptible of variations to a much greater extent indeed than that of the more imperfect animals; but fill within certain limits. Beyond thefe limits the principle of vegetable, as of animal life, refifts any further change. Thirdly, the heat of vegetables varies, according to the temperature of the medium in which they are, which we difcover by varying that temperature, and oblerving the heat of the vegetable. Fourthly, the expence of the vegetating powers in this cafe is proportioned to the neceflity,

and the whole vegetable powers may be exhaufted in this way. Fifthly, this power is molt probably in proportion to the perfection of the plant, the natural heat proper to each fpecies, and the age of each individual. It may alfo perhaps depend, in fome degree, on other circumstances not hitherto obferved; for in experiment II. the old fhoot did not lose its powers, while that which was young or growing did; and in experiment III. and IV. we found that the young growing shoot of the fir was with great difficulty frozen at 10°, while a bean-leaf was cafily frozen at 22°; and in experiment V. the young fhoot of the fir thawed the ice at 28°, much fafter than the leaf of the bean. Sixthly, it is probably by means of this principle, that vegetables are adapted to different climates. Seventhly, that fufpenfion of the functions of vegetable life, which takes place during the winter feafon, is probably owing to their being fufceptible of fuch a great variation of internal temperature. Eighthly, the roots of vegetables are capable of refifting cold more than the ftem or leaf; therefore, though the ftem be killed by cold, the root may be preserved, as daily experience evinces. The texture of vegetables alters very much by the lofs of life, especially thofe which are watry and young: from being brittle and crifp, they become tough and flexible. The leaf of a bean when in full health is thick and maffy, repels water as if greafy, and will often break before it is confiderably bent; but if it is killed flowly by cold, it will lofe all thefe properties, becoming then pliable and flaccid; deprived

of

of its power of repelling water, it is eafily made wet and appears like boiled greens. If killed quickly, by being frozen immediately, it will remain in the fame fate as when alive; but upon thawing, will immediately lofe all its for mer texture. This is fo remark. able, that it would induce one to believe, that it loft confiderably of its fubftance: but from experiment VI. it is evident that it does not. The fame thing happens to a plant when killed by electricity *. If a growing juicy plant receives a ftroke of electricity fufficient to kill it, its leaves droop, and the whole becomes flexible.

So far animal and vegetable life appear to be the fame; yet an animal and a vegetable differ in one very material circumftance, which it may be proper to take particular notice of in this place, as it fhews itfelf with remarkable evidence in thefe experiments. An animal is equally old in all its parts, excepting where new parts are formed in confequence of difcales; and we find, that thefe new or young parts in animals, like the young hoots of vegetables, are not able to fupport life equally with the old; but every plant has in it a feries of ages. According to its years, it has parts of all the fucceffive ages from its firft forma. tion; each part having powers equal to its age, and each part, in this refpect, being fimilar to animals of fo many different ages. Youth in all cafes is a state of imperfection; for we find that few animals that come into the world

in winter live, unless they are particularly taken care of; and we may obferve the fame of vegetables. I found that a young plant was more eafily killed than an old one; as alfo the youngest part of the fame plant.

This power of generating heat feems to be peculiar to animals and vegetables while alive. It is in both a power only of oppofition and refiftance; for it is not found to exert itself spontaneously and unprovoked; but must always be excited by the energy of fome external frigorific agent. In animals it does not depend on the motion of the blood, as fome have fuppofed, because it belongs to animals who have no circulation; befides, the nofe of a dog, which is nearly always of the fame heat in all temperatures of the air, is well fupplied with blood: nor can it be faid to depend upon the nervous fyftem, for it is found in animals that have neither brain nor nerves. It is then most probable, that it depends on fome other principle peculiar to both, and which is one of the properties of life; which can, and does, act independently of circulation, fenfation, and volition; viz. that power which preferves and regulates the internal machine, and which appears to be common to animals and vegetables. This principle is in the moft perfect ftate when the body is in health, and in many deviations from that ftate, we find that its action is extremely uncertain and irregular; fometimes rifing higher than the standard, and as

other

other times falling much below it. Inftances of this we have in differ. ent difeafes, and even in the fame d feafe, in very fhort intervals of time. A very remarkable one fell under my own obfervation, in a gentleman who was taken with an apoplectic fit; while he lay infenfible in bed, and covered with blankets, I found that his whole body would, in an inftant, become extremely cold in every part; continue fo for fome time; and, in as fhort a time, he would become extremely hot. While this was going on for feveral hours alternately, there was no fenfible altera. tion in his pulfe.

pared from them, allowed him a glafs of wine or a little beer occafonally, but chiefly to confine himfelf to water. He purfued the plan very fcrupulously, loft his redundant fat, grew active as ufual in about fix months. I recommended a perfeverance for a few months longer; then to allow himfelf light animal food once or twice a week, and gradually to fall into his ufual way of living. He grew well, and continued fo.

woman,

A young unmarried about twenty three years of age, of a low ftature, and very fat, applied to me for affiftance in a great difficulty of breathing, fomnolency, and incapacity for any exercife. It was a hardship to her to be obliged to go up ftairs, and at laft to crois the floor of her apartment.

It seemed to, me that mere obefity was her principal malady; indeed fhe had no other complaint but fuch as apparently might be accounted for from this fuppofition. She was ordered to purfue vegetable diet, and in the fummer to drink the waters at Scarborough. She conformed to thefe directions, became more agile, lefs fleepy, lefs averfe to exercife. She walked up the fteps at Scarborough from the paw, a talk of no little difficulty to people much lefs er cumbered. I urged a continuance of the fame diet: fhe was diffuaded from it by her friends, and died of fat in the twenty-feventh year of her age. She left permiffion with her filter, to be opened, if it was defired: the cafe was too fingular to be neglected: all the vicera were perfectly found, but larded with fat beyond apprehension. In dividing the external teguments,

we