« VorigeDoorgaan »
following the opinion of Dr; Franklin, maintained the superior merit and efficacy of those which were more elevated, and pointed: this opinion was followed in the conductors fixed on the powder-magazines at Purfleet : and the memoir now before us, contains a considerable number of experiments, that confirm it in the strongest manner. The result of these experi, ments may be contained in the following propositions :-That it is erroneously asserted, that the pointed conductors draw the lightning fooner from the clouds, than those whose extremities are blunt, obtuse, and present a sort of a round knob--for the contrary happens in fact :-- that this error arises from confounding the property of silently drawing fire from the clouds, with that of exciting lightning, two things which are very different, as M. Le Roy abundantly proves, in this memoir :-that the conductors being designed, by their form, to draw the fulminating matter from all the parts of the building on which they are erected, ought, for that reason, to be pointed, and to be raised to a certain height above the building :--and that, finally, should an explosion of lightning fall upon these conductors, its effects would be much less violent, than if it fell upon the others.
ANATOMY. Memoir I. Obfervations on the Situation of the Liver, in its
natural State, together with Remarks on the Manner of perceiving several of its Disorders by the Touch. By M. PORTAL.
In order to acquire, by the touch, a certain knowledge of the disorders of the liver, it is necessary to ascertain, by a series of observations, its situation, which differs according to the age and attitudes of the patient, and which is also modified by seves sal maladies, which do not immediately affect the gland itself. The liver is larger in the fætus than in children newly born, The stomach of the former, which was perpendicular, becomes gradually almost horizontal : the left lobe of the liver, when deprived of the blood, which was conveyed thither by the un. bilical vein, diminishes considerably in size: M. Portal oba ferves farther, that this is not the only change occasioned by the revolution, which takes place in the circulation of the blood at the period of birth : the pelvis assumes gradually another form, the lower extremities, which receive a greater quantity of blood, grow in length, and acquire a new degree of strength and conlistence. The form of the bason in the fætus, and the smallness of the lower extremities, are favourable to delivery : the child in the firft period of life, when its weakness will allow it nothing beyond a kind of reptile motion, is so constituted, as to go on hands and feet; but as soon as the legs acquire Strength, fufficient to support the body in an erect posture, their
proportion, proportion, and that of the thighs change ; and all these changes, which are the necessary consequences of a change of circulation, seem evidently to have been prepared and combined by the Author of Nature for the advantage of the human frame,
The growth of the liver is not proportionable to that of the other parts of the body. In persons who have arrived at a mature age, it lies entirely concealed under the spurious or baftard ribs, when they are placed in a horizontal situation. When they are in a different or erect position, the liver becomes perceivable, and this is therefore the situation that must be preferred, as the most adapted to exhibit, to the touch, the true state of that gland.
The liver acquires a monstrous volume by the excessive use of food, as appears from the experiments that have been made on animals. Stoppages, or obstructions in the lungs, change the ficuation of the liver, which, in these circumstances, extends itself under the ribs; but we must not, according to Mr. Portal, conclude from hence, that the liver is attacked : this is an error, into which he acknowledges that he has sometimes fallen, but the diflection of bodies undeceived him.
The liver, says our Author, is not the only part of the body that changes its situation in different altitudes. M. Portal observes, that the anterior part of the bladder, in a man who Hands upright, corresponds with the same parts of the abdomen, to which the bottom of the bladder corresponds in a man who Jies in a horizontal posture. This remark may be of considerable use and importance in medical practice. Such is the refult of M. PORTAL's memoir, to which we refer the Reader for farther details and illustrations, relative to this interesting object of anatomical investigation, which he will find here very amply and accurately described and considered. MEMOIR II. Concerning an extraordinary Pregnancy. By M.
HALLER. This memoir contains the history of a woman, who, after having discovered all the symptoms of pregnancy, which the reckoned from the beginning of the month of June 1763, fell into a state of infirmity and languor, in which all these symptoms totally dilappeared. She recovered her health in the month of May 1764: and she exhibited no marks of weakness or indisposition until July 1772.-She died in August, that year, after a violent fever, which lasted seven days, and was accompanied with intense pains. On opening the body, a kind of rack or tumour was found, which communicated with the uterus by the ilium on the right, and a part of the os facrum. This sack, which had within it the right tube and ovaria, contained a foetus of seven months, whose putrefaction had occasioned the death of the woman ; however, the circumstantial
mentation of thining a noths after." was, indee
account which is here given. of her disorder and pregnancy, proves evidently, that the fetus had been without life from the month of January 1764. Notwithstanding this, the woman enjoyed a perfect state of health during eight years, with this lifeless mass in her body, and barrennels seemed to be the only effect it produced in the animal æconomy. M. HALLER mentions it as a circumstance worthy of notice, that after having suffered pains that seemed to indicate a miscarriage, in January 1764, which may be considered as the time of the death of the fætus ; the woman suffered again pains of a like nature, at the period which, according to the proper calculations, would have brought on the delivery; he observes farther, that at this period she had milk, which was, indeed, foon disa fipated, but returned two months after. Memoir III. Concerning a new Method of ferforming the A11
putation of the Extremities. By M. Portal. . This memoir is designed to prevent the inconveniencies that arise frequently from the ordinary method of amputation, after which a part of the bone still remains jutting out. This not only renders often a new operation necessary, but also makes the cure difficult, exposes to dangerous accidents, and even after the cure is finished, prevents the stump from being covered with felh, which is attended with several disagreeable circumstances. We shall not enter into a particular analysis of this memoir, which might be obscure without the allistance of the cuts that accompany it. We shall only mention the fact upon which M, PORTAL founds his new method, and shew, in a few words, in what this method essentially consists. The fact is, that the soft parts of the human body are almost all susceptible of contraction, after being cut; and this, though in a smaller degree, is observable, even in dead bodies. This contraction, or rather contractibility, is different in different parts of the human frame: it is strong and intense in the skin, the adipose membrane, the tendons, the aponeuroses of muscles, in the veins and arteries ; and its most powerful effect is produced in the moment of the separation of the parts, thougla even after this separation, it remains in activity for a considerable time. It must, consequently, happen after the amputation of a member, that the soft parts, farinking in, leave the bone uncovered; and that the different parts, suffering a greater or Jess contraction, the wound assumes a pyramidal form, which renders the dressing more embarrassing, and the cicatrization more difficult.
If therefore (to come to what M. PORTAL proposes) the muscle be cut in the moment of its greatest contraction, it will Thrink less than if the amputation had been made at the time of its greatest dilatation or extension, and a more considerable part
of the muscle will remain after the amputation, than if the operation had been performed when the muscle was contracted. It is, however, to be remarked, that of the muscles which are placed on the two sides of the bone, those, on one fide, are contracted when the member is stretched out, and dilated or diftended when the member is bent or folded; while those, on the other side, are diftended when the member is stretched out, and contracted when it is folded or bent inward :- the consequence deducible from this, is, that the member must be stretched out during the amputation of the former, and folded, contracted, or bent inward, during that of the latter. IV. A SECOND Memoir Relative to the Anatomy of Birds. By
M. Vice-D’AZYR. In the first memoir, this ingenious Academician, who has formed a high idea of the importance of the anatomical observations that may be yet made upon the structure of birds, laid down the plan, which he continues to execute, fixed the genera or classes that form the basis of his researches, indicated the new nomenclature, which he employs in his descriptions, and divided into twenty-four regions, the different parts of the body of a bird. In the first memoir, he described the anterior thoracic region, the region of the clavicle or collar-bone, and that of the shoulder-blade. In the second memoir, now before us, he examines the state of eleven regions, viz. the higher region of the shoulder, .the internal and external regions of the humerus, the internal and external regions of the cubitus, or that part which supplies the places of a fore-arm and hand, the superior region of the back and neck, the inferior region of the neck, the superior and lateral regions of the cranium or skull, the inferior region of the head, and that of the surface of the skin. Ten regions more are to be exhibited and described in a following memoir. The details contained in this memoir are certainly curious and interesting; and the mechanism, that produces the various motions of the winged tribe, is displayed with great perfpicuity. It is more especially worthy of observation, that in comparing the muscles and bones of birds, with those of the human species, the analogies are found to be much greater, and more striking, than could have been expected conlidering the little resemblance there is between the external forms of these two classes. This thews the beautiful uniformity that reigns in the great scheme of nature, and that in orders of Being so different: it is also a remarkable proof of final causes, when we consider, that the diversities in this otherwise uniform plan, are exactly suited to the nature, structure, and motions, that characterise each class,
CHYMISTRY. MEMOIR I. New Observations on the Analysis of Crystals of Vera
degrije and Salt of Lead, relative to the Air that is combined in these two Mixts, and considered as one of their constituent Prine ciples, -as also on a Copper and Saline Sublimate, which the Verdegrise yields in a certain Period of the Anal/is. By M. DE LASSONE.
The operation, by which the acetous fpirit, called Radical Vinegar, is obtained by distilling verdegrise, or crystals of verdegrise, has been often repeated; but the phenomena which accompany this operation, have not, in the judgment of M. De LASSONE, attracted sufficiently the attention of chymical observers. He had formed the design of ascertaining the following fact, that during the distillation of crystals of verdegrise, and salt of lead, a fluid escapes, of the nature of those which the ancient chymists called Gas, and to which the moderns give more commonly the appellation of Air ; but as there escaped also, towards the end of the operation, acid vapours under a visible form, it became necessary to examine the result of his distillation, before the moment in which these vapours begin to appear. When M. De LASSONE compared the weight of the product and refiduum of the distillation, with the weight of the verdegrise that was employed in this experiment, he found that the latter was considerably diminished, and that consequently a proportionable quantity of Gas had escaped, or disengaged itself in the operation.
By interrupting thus the distillation at a certain period, our Academician observed circumstantially and fully a fingular fact, which had been perceived before by some chymists, but in a cursory manner. The neck of the retort, employed in diftilling the crystals of verdegrise, contained a solid, light, and white substance, which assumed a yellowila colour when it was exposed to the air. This substance, on examination, appears to be a copperish, volatile salt, entirely diffolvable in water ; if, the distillation be continued, the acid vapours, highly concentrated, which pass towards the end of the operation, diffolve this salt and carry it along with them; and of consequence, the copperish Aowers are only to be obtained, when the distillation is suspended, the moment before the acid concentrated vapours appear under a white form.- Before this period of the operation, the radical vinegar contains no copper; it only begins to contain some, when the copperish flowers, carried along by the acid vapours, mix themselves with this vinegar: if it is then rectified by a new distillation, these Aowers are no more sublimed, and therefore, a radical vinegar, exempt from copper, may be extracted from verdegrise: however, the radical vinegar, obtained by this process, cannot be looked upon as absolutely