of its powers as old age advances. Effects of healthful ftimuli on the fyftem. Property of gastric juice in diffolving dead fleth, while it lofes its power upon living fleth. Exemplified by the curious facts, first noticed by Mr. John Hunter, of the ftomach itself after death, being corroded by the gaftric liquor. Hunger probably proceeds from the ftimulus of the gastric menitruum on the nerves of the stomach. Powers of the living principle preferved and improved by moderate exercife; diminished and exhaufted by too violent exertions.-Reftored by food and reft. Habit increafes in a wonderful manner the active power of parti cular nerves, exemplified in dancing, playing upon mufical inftruments, &c. Great ftrength of body ufually attended with a diminution of the mental powers, and vice verfa; hence the debilitated body, and difeafes incident to ftudious. and fedentary perfons. Great and fudden effects of the paffions on the living principle.

Powers of the living principle uniformly and uninterruptedly conveyed to every part of the body. All the mufcular fyftem replete with it, and fo tenacious of it, that it remains for fome time after the death of the animal. This time different in different animals. In man and quadrupeds, whofe organs of refpiration are of the fame kind, a fhort time. In frogs, vipers, eels, turtles, and other amphibia, for a longer period, and may be renewed by ftimulus, as appears from various experiments.

We fhall conclude mentioning our Author's obfervations on the living principle, by tranfcribing part of the thirtyfixth paragraph, because it gives an ingenious folution of fome phænomena in the animal oeconomy, and in a manner which we do not recollect to have met with before.

It not unfrequently happens, during the last efforts of nature for the continuance of life, that flight convulfive motions of the mufcles, particularly of the eyes and face, precede death. This effect probably arifes from their vicinity to the principal feat of the living powers. But the more remote mufcles are not affected; for from the want of a fufficiency of life, they are incapable of being acted upon. In fuch cafes, after death, the mufcles are found to be in a relaxed ftate, being foft and flexible," &c.

From this analyfis of what Dr. Gardiner fays of the liv ing principle, it is evident, that the medical reader will find much entertainment from this part of the performance at large. But in what light the metaphyfician or the divine will confider what is here faid of the living principle, is what we cannot take upon us to determine. It may naturally be afked; Is there a principle of life in the body distinct from the immaterial principle? This is a point we do not mean to enter into a difcuffion of. All we fhall obferve

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ferve is, that the feveral phænomena ascribed to the living principle, do not appear to us in the leaft inconfiftent with the idea of its being immaterial. The renovation of mufcular action in fome animals after death; is not a renewal of the living principle, but merely a renewal of a mechanical action, the effect of which exifts for a longer time in fome animals than in others, even after the primary cause of it is removed.

The second section treats of the nerves, of sympathy, and of Stimuli.

Sympathy exifting between all parts of the body, arises probably from the unity of fubftance between the nerves and the brain. Anomalous fympathies not fatisfactorily accounted for from the anaftomofes, or connections of the nerves with each other-owing to morbid irritability. The ftomach, the principal feat of the most remarkable sympathetic affections which happen in valetudinary ftates of the body.

Healthy ftimuli are fuch as by their action fupport the living principle. Noxious ftimuli, fuch as deftroy or leffen it. The most powerful and falutary remedies most likely to become noxious ftimuli. Stimuli lofe their powers on certain perfons by habit. Some stimuli a&t imperceptibly on the body, and yet occafion the most confiderable changes in the fyftem, either in producing difeafes, or reftoring health. Inftances-putrid marsh-miafmata-effect of Peruvian bark -neceffity of fome ftimuli producing their effects without consciousness-nerves of the fkin from their number and fenfibility most likely to be affected by the viciffitudes of heat and cold.

The nerves of the stomach, and bowels fubject to a greater variety of imperceptible ftimuli, than those of any other part of the body. The effects of morbid ftimuli conveyed to distant parts with the fame unconfciousness of the ftomach being affected-In delicate conftitutions certain. ftimuli are capable of producing a fufpenfion of the animal actions. Thus fainting from flight caufes-whole fyftem affected from flight and even agreeable ftimuli applied to the olfactory nerves, in irritable female habits. A blow on the pit of the ftomach may induce a fufpenfion of the vital powers, and even death itfelf, though upon examination after death, that vifcus fhall not appear to have fuffered in its texture-Infenfibility, and often death, from a blow on the head, without any apparent injury done to the skull or brain-Every fudden and unexpected pain more dangerous than that which is gradually brought on-inftance the great degree of pain the human body is often capable of bearing be

fore

fere diffolution, in many cruel modes ufed in fome countries of putting malefactors to death. Affections of the mind influence the body, and vice verfa-thus in chronic diseases, attended with præternatural irritability of the nerves; the paroxyfm fufpended for a time, while the mind has been under the influence of fome particular paffion or violent emotion :-hence the neceffity and great ufe of keep ing the mind conftantly employed either by business or amusement in the cure of certain difcafes. Effects of opium and of poisons communicated by fympathy. In habits where the admiffion of opium into the ftomach, in whatever dofe or form it may be given, affects the patient difagreeably, it fhould be injected into the rectum by glyfter-nerves of the rectum bear opium in larger quantities than those of the ftomach. Deadly effects of the lauro-cerafus; though its leaves boiled in milk may be taken with impunity, yet from the poffibility of its producing accidents in children and delicate conftitutions, ought to be banished from every species of cookery. The mode in which the vegetable poisons operate not to be learnt by the infpection of the body. The obfervations on this point are fo judicious, and fo neceffary to be known by all practitioners, particularly with refpect to juridical information; that we cannot better close this account, which this accurate writer gives of the effects of fympathy, than by giving the whole of it to our readers.

'When undoubted information is received that the deceafed had taken a deleterious fimple, or compofition, in fuch quantity as is known to prove a poifon to the human body; that, immediately after it was fwallowed, fuch fymptoms arofe as are ufually the confequence of the poifon exhibited; that thefe fymptoms increafed in violence, and continued till they produced death; on fuch occa fions there can be little doubt as to the caufe; and if part of the poifon is (be) found in the ftomach and bowels, the evidence amounts to a demonftration. But without thefe circumftances, in our judicial declarations, we can prove nothing from any appearance of the body on diffection: for the fuffufion of blood fometimes obferved in different parts of the body, particularly about the face, neck, and breast, from the small veffels of the fkin, is no more than what happens in almoft every cafe of fudden death, and even takes place fometimes on a ftop being put to the circulation, on the demife of people after chronic difeafes. Neither do thofe flight degrees of redness, from the blood ftagnating in the small veffels of certain parts of the ftomach and bowels, after death, prove that any thing is unnatural, or characteristic of particular poifons. All must be referred to the particular operation, of the poifon on the nerves of the ftomach, by which their power of conducting the principle of life is deftroyed. Its effects are by general fympathy, quickly communicated to the rest of the fyftem,

and

and produce a fufpenfion of all action, but without making the fmalleft apparent alteration on the structure of the nerves or other parts." In the third fection Dr, Gardiner proceeds to confider the effects of heat and cold.

The writer first takes a review of Dr. Crawford's ingenious theory upon this fubject; and although he agrees with him in his general principles, yet he differs with him in his imode of reasoning, and argues against the manner in which the Doctor fuppofes the animal heat to be fupported.-He admits the double exchange of the principles of heat and phlogifton in the lungs, but cannot conceive how this Thould become the fource of animal heat in the circulation; a circumftance accounted for by Dr. Crawford; by obferving that the blood in the course of the circulation abforbs a great quantity of phlogifton, and is thereby obliged to part with a portion of its heat. Dr. Gardiner fuppofes, on the other hand, that part of the fire extricated from the air in the lungs is expended in converting the moisture accompanying refpiration into vapour, and that the rest is abforbed by the blood, which, in circulation, gradually undergoes fuch a change from the ftate it poffeffed in the large arteries, as leffens its capacity for containing abfolute heat, and of courfe there will be a gradual extrication of part of that fire it held.

The author likewife differs from Dr. Crawford with re gard to the mode in which that power in animals is produced, by which they are enabled to maintain nearly the fame temperature in different degrees of heat; which the latter thinks is owing to the degree of heat in which the animal is placed, diminishing proportionally the attraction of the blood for phlogiston.

The writer alledges, that from the commencement of animal life there is a conftant generation, and a constant confumption of heat; this takes place after birth :-Deficiency in the organs of the foetus for generating heat, fupplied for a time by the mother. Generation of heat commences with refpiration, illuftrated by the process of incubation, admirably well detailed here. Review of the experiments recorded in the Philofophical Tranfactions, concerning the degree of heat the human body was able to bear without any fenfible inconvenience, and which induced an opinion, that the living body poffeffed a power of resisting for a time any addition or diminution of heat above or below the healthy ftandard. The author contends, that the living body poffeffes no fuch power of refifting or destroying heat, when placed in an air heated greatly above its own temperature. This circumftance Dr. Gardiner accounts

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for in a more fimple and fatisfactory manner; obferving that this balance of heat and cold, and the prevention of any remarkable change in our temperature, is accomplished by various actions being by turns excited in the body for the production of heat or cold, and for that degree of either which beft correfponds with the exact regulation of the ftandard heat. In temperate air, thefe operations carried on with fuch cafe, that no fatigue is experienced from their continued action. In air extremely hot or cold they act with a degree of violence on the body, and the fyftem is ex, cited to fuch actions as correfpond with the nature of the ftimulus. Exemplified by a review of the effects of heat applied to the body as ftated in thefe experiments.

Pulfe quickened, and perfpiration increased-heat produced and increafed by acceleration of circulation; this if fuffered to accumulate would deftroy the animal-hence the neceffity of a fweat being produced, which contributes greatly to carry off the furplus of heat. Loofe fpungy texture of human body makes the admiffion of heat into it gradual and flow; its bulk too, fuppofing it a mafs of inanimate matter, would require a confiderable time to be heated thoroughly to a few degrees above its temperature. As animated, na ture is employed in counteracting the effects of the heat by the refrigerating process of sweating, and the confequent expenditure of heat in the formation of vapour. Powerful effects of evaporation, exemplified by the practice of cooling wine in hot countries, by wrapping up the bottles în wet cloths, and hanging them up in the fun, and by other cu rious facts.

The powers of life proportionally exhaufted by an accumulation of heat above the natural standard,-Bodies in which heat is accumulated refift for a time the effects of cold air; hence the gentlemen who were fo overheated in the experiments, felt no inconvenience from exposure to cold air. But they experienced more or lefs of debility and languor, trembling of the hands, and other fymptoms, all fhewing, that while they remained in this heat, there was an uncommon exertion of the powers of life in obviating the effects of it, and that by a continuance of the fame procefs thefe powers may be totally exhaufted. Cautions against cooling the body too fuddenly after being overheated.

Power of living bodies to refift cold as well as heat. Animals poffefs a power, according to Mr. John Hunter, of generating heat for this purpofe. Principle of life begins to decline when an animal body, or part of it is cooled confiderably below its ftandard heat, and continues declining till totally extinguished-recovered by gradual admiffion

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