scurvy or not he is still of opinion that scurvy arises from a
defect of oxygen in the system, and that the vegetable acids
operate in curing it by supplying the want of this principle:
but this conjecture is by no means satisfactorily proved. Much
may be likewise done, in effecting a cure, by fresh animal
food, as well as vegetable; and many of the substances, which
afford oxygen in the largest quantity, are found insufficient for
curing the disease; as, for example, the mineral acids. Some-
thing, it appears, must be attributed to the radical as well as
to the acidifying principle.

The last chapter treats on the subject of the malignant
ulcer, which so often appears in sailors from very trivial ac-
cidents, as slight cuts or scratches; and which so much re-
sembles that which sometimes shews itself in hospitals. Dr.
Trotter considers it as depending very materially on the use of
spirits, to which sailors are so much accustomed, and on the
want of pure air. He is not able to recommend any effectual
mode of treatment, but is disposed to agree with Dr. Mitchell
in the idea of its being of an acid nature, and therefore
capable of being removed by alkalis, such as the carbonate of
potash. The supposed production of this disease does not
seem reconcileable to that tendency to scurvy, which foul air
and irregularities have been, in similar circumstances, calcu
lated to excite.

Having thus made a few observations on some of the more important parts of this work, it would be injustice to the author to take leave of it, without bearing testimony also to his earnest endeavours to improve the situation of Navy S⚫geons and Mates; whose encouragement is not yet sufficient for the nature of the important services which it is their duty to perform. Indeed we have pleasure in admitting, that Dr. Trotter appears to be animated with a most ardent zeal for the service of his country; and in retiring from his public duties, he has the prospect of enjoying the approbation of all those who are acquainted with his active exertions in the Navy. It is impossible for us to correctly appreciate the various obstacles and discouragements which the Doctor has experienced, in the course of his attempts at reform: but, howmuchsoever he may have been chagrined by them, we hope

bractica that he will reflect on the impossibility of avoiding this fate in

such a career, and that he will have his ample reward in the
testimony of an approving conscience.

Yell.

ART. XII. Elements of Galvanism, in Theory and Practice; with a comprehensive View of its History, from the first Experiments of Galvani to the present Time. Containing also, Practical Directions for constructing the Galvanic Apparatus, and plain systematic Instructions for performing all the various Experiments. Illus trated with a great Number of Copper plates. By C. H. Wilkinson, Lecturer on Galvanism in Soho-square, Member of the Royal College of Surgeons, &c. &c. 2 Vols. 8vo. with Plates. 11. is. Boards. Murray. 1804.

SINCE

INCE the period at which Galvani first discovered the effects of metallic influence, in producing muscular contractions in dead animals, an immense number of curious and interesting facts on the same subject have been brought forwards; and a new science thus seems to have sprung up within a few years, possessing a considerable variety and extent, and promising to reward the labours of the philosopher by inductions of high interest and importance. If our expectations have not yet been fully realized, we may still hope that time, and a fortunate concurrence of circumstances, will throw more light on the nature of Galvanism, and establish its utility in various obstinate diseases to which it has been supposed that it might be successfully directed.

The author of this production has performed an acceptable service to the public, by collecting and arranging the various facts and doctrines which have appeared in different quarters, on the subject of Galvanism, and thus affording a connected view of the progress and present state of this science. The analysis of every work and memoir, of any consequence, which relates to this influence, is given at considerable length: but though this amplitude of detail is not without its use to the student, it has nevertheless made the publication more than necessarily diffuse.

The first volume, and nearly one half of the second, are occupied with an account of the principal facts and reasonings relating to Galvanism, which were adduced both before and after the discovery of the Voltäic Pile. Some of the most singular are those mentioned by Aldini, the nephew of Galvani, on the mode in which this influence is capable of being excited. He found that the simple contact of the nerves with the muscles is sufficient to produce contractions, without the interposition of any metallic substance; and hence he concludes, with Galvani, that there is a peculiar fluid, inherent in the animal machine, which is capable of producing this phænomenon, independently of the influence of metals, or of any foreign cause. His experiments were made by bringing the denuded sciatic nerves into contact with the muscles of the thigh, deprived of their integuments; when contractions,

similar to such as occurred in the customary Galvanic experiments, were immediately produced. By the influence of warm blooded animals, he was also able to excite convulsions in the cold. For this purpose, a finger of the operator, moistened in salt and water, was thrust into one of the ears of an ox recently killed; the nerve of a prepared frog, held in the other hand, was then made to approach the tongue of the ox; and, at the instant of contact, convulsions were excited. Contrary to the observations of most other experimentalists, Aldini found that the heart was not affected by Galvanism..

The experiments of Galvani first drew the attention of scientific men to the existence of a till then unknown influence, capable of being generated in different ways. It had ceased, however, to produce any considerable interest, when the discovery made by Volta, of a mode of concentrating Galvanic influence, by a series of metallic plates properly disposed, renewed a lively sensation in the philosophical world, and again excited to this subject a vigorous attention. Till the period at which this discovery was communicated, Physiologists had turned their attention entirely to the disturbance of the muscular fibre. In increasing the scale of their experiments, they confined themselves altogether to the augmentation of the animal substances employed. With this view batteries of frogs were arranged; but no idea seems to have been entertained of what was to be expected from an increase of the series of metals.' The mode of constructing the pile was from time to time considerably improved: but it was at length found, that the readiest and most effectual mode of exciting the Galvanic influence is by means of a wooden trough, with transverse grooves made in it, into which are inserted alternate plates of zinc and copper, cemented together in such a way as to prevent the cells from communicating. Into the cells is poured a solution of an acid, alkali, or neutral salt, but generally the former; and, on completing the communication between the extremities, a shock is felt or a spark seen. When an acid is used, the oxyd, which is formed on the zinc, is dissolved; and thus the plates are kept clean, without the necessity of removal from the trough.

Soon after the important communication of Volta on the selfcharging power of his moto electric apparatus, the celebrated French chemists, Fourcroy, Vauquelin, and Thenard, supposing à priori that the effects would be in proportion to the metallic surfaces exposed, constructed plates of zinc and copper about nine or ten inches in diameter. The plates which had been previously employed, rarely exceeded the size of half-a-crown. As one of these large plates

exposed

exposed a surface about 40 times greater than that of the small plates, it was expected that the effects produced from ten such plates would have equalled the effects of four hundred of the smaller ones; but, to their great surprize, the above experimenters found that the sensations were the same, from an equal number of each; and that the extent of surface did not make any sensible difference. The power appeared to be regulated by the number of the plates, and not to be influenced by the surfaces exposed. They were equally surprized, when they found that a series of ten large plates, the effects of which on the human frame could with difficulty be perceived, possessed a power of burning finely drawn wires, and of deflagrating laminated metals, such as gold and silver leaves, equal to that of four hundred smaller plates, the sum of whose surfaces was equal to the surface of the larger ones. These curious facts led to an important deduction, that the influence of the galvanic fluid on the human frame, is in pro portion to the series, or number of the plates employed; while its effects on metals are in the ratio of the surface exposed.'

We deem it unnecessary to go farther in our relation of the ample details given in this work, on the diversified mode in which Galvanic influence is excited, and on the different hypotheses which have been formed to account for it. We shall pass on, therefore, to the chapter which treats of the Influence of Galvanism on the Animal Functions.-It appears to the author, that respiration is the function in which this influence is most concerned; for he considers it as an important Galvanic operation, and the lungs themselves as affording a wellmarked instance of a structure similar to that of the electric organs of the Torpedo. By the constant succession of shocks which is supposed to be communicated from the lungs, a stimulus is afforded to the organized and animated parts' of the body, by which heat is produced, and the other animal functions enabled to be properly exercised, without the necessity of having recourse to the irregular and unequal action of respiration; the unstable and uncertain exercise of which would place the system in a very dangerous predicament:

'On every exertion, and on every sudden alteration of temperature, the secretions would vary; and the body would be in a state of constant changes. Is this consonant with the uniformity, the admirable regularity which is observed? with the inherent power, the vis medicatrix nature, which acts equally against excessive heat or intense cold? If these changes should be too violent for her efforts to withstand, her preserving temperature can only be destroyed by the destruction of life also.'

A half crown measures about 1 inch in diameter, and the diameters of the large plates being estimated at 10 inches, as the areas of circles are in proportion to each other as the squares of their diameters, the ratio will be as 100 are to 24, or as 1 is to 40.'

Mr. W. informs us that he considers his doctrines as something more than a "rudis indigestaque moles." He offers them as the result of long and mature reflection; and he says that they received so little opposition, when read before several of the London Medical Societies, that they are regarded by him as completely stamped with the approbation of the learned mem bers. Without meaning to throw any kind of improper reflection on the societies to which the author alludes, we should be inclined to doubt whether the little opposition, which his doctrines received, could form an unequivocal proof of ap probation; and even if it be so considered, we should not be disposed to concede so much weight as the author assigns to the opinions of the gentlemen who in general compose the attending part of such societies. They are mostly young men; and though they may be very earnest in the prosecution of their studies, they cannot in general be supposed to be yet extensively acquainted with physiology, or to have acquired any considerable portion of scientific authority.

When a doctrine is offered with such pretensions as are here advanced, we naturally expect a luminous and well digested account of a variety of circumstances which support or confirm it. We are therefore surprized to find a remarkable paucity of evidence in its favour, and must regard it, at present, as little more than a crude speculation. The author relies much on a supposed similarity between the structure of the lungs, and that of the electric organs of the torpedo; though he admits that, in the latter, ، an external circuit is required,' while in the former the electric changes of the pulmonary cells are equalized by the pulsatory current of the blood.'

Mr. Wilkinson considers the present doctrines of respiration as insufficient for the purpose of accounting for the changes which the blood undergoes in the lungs, and for the production of animal heat. He examines, at some length, the statements of the English and French Philosophers on these subjects, particul rly those of Crawford and Lavoisier; and he concludes that their doctrines are not the results of accurate induction. He is of opinion that the absorption of oxygen is insufficient to account for the regular production of animal heat, and for the equable temperature which the body is capable of preserving under a very extensive thermometrical range. He justly observes that the different states of density in the air are inadequate to supply the quantity of oxygen necessary for affording the heat required to keep up an equable temperature in a high latitude: but he seems to found the necessity for the agency of electricity in this process, on the supposition that the insensible perspiration is the same, or nearly the same, in

all