From the divifions of the branchial arteries into exceedingly minute branches, we fhould fuppofe, that the force of the ftroke of the heart upon the blood must be very much broken and loft before the blood gets into the branchial veins; and in fact I faw no pulfation in the branches of the aorta of a living fkate. Hence, in the first place, we may infer that the branchial veins are not made thick and tough, merely to enable them to reûft the vis à tergo.

As fo much ftrength and elafticity in the branchial veins are not neceffary for merely refitting the force of the blood, or that more ftrength and elafticity, than we obferve in our pulmonary veins, were not neceffary for receiving or for merely conducting the blood to the other parts of the body, we muft fuppofe that these thick, tough, and claftic coats are of a living mufcular nature, and that the progreffion of the blood through the reit of the body of the fish depends much on their activity. We fhall ftill more readily admit that the mufcular power of the veffels, and particularly of the arteries, is neceffary for the progreffion of the blood, when, proceeding a flep farther, we obferve a third circle completed in the liver.

Applying to man what we have obferved of the veffels and circulation in fishes, we in the first place receive ftrong confirmation of an opinion I have always taught, That our arteries are of a muscular nature; and that their activity is effential in circulation, fecretion, and other important offices.

In the next place we conclude, that the alternate preffure of the diaphragm and abdominal mufcles in refpiration, is not, as fome, have fuppofed, the principal caufe of the motion of the blood through the liver; but that the motion of the blood and fecretion of the bile depend chiefly on the mufcular structure and action of the vena portarum.'

The glandular organs and fecreted liquors come next under the Doctor's confideration, and here the reader will find much matter of curiofity; fome erroneous theories are, with reafon, rejected; efpecially fuch as have been built on principles that are not founded on facts or experiments.

The three following chapters contain defcriptions of the lymphatic fyftem, with fome obfervations on the ufe of the spleen. Here again our Author refutes the opinions of former anatomifts. • Mr. Hewfon,' he fays, appears to have left this part of phyfiology involved in nearly the fame obfcurity in which he found it."

In the fubfequent chapter, Dr. M. attempts to establish his claim to the firft difcovery of the existence of the lacteal and lymphatic systems in birds and amphibious animals as well as fifhes, in oppofition to Mr. Hewfon's pretenfions: as far as we are able to judge of the matter in difpute, from what is here advanced, Dr. M. feems to make good his claim.

After defcribing the brain and nervous fyftem, our Author proceeds to the organs of fenfe. In all fifhes, external openings or noftrils for fmeiling are very evident; generally two on each fide, leading to a complex organ, the furface of which is of con

L 4

fiderable

fiderable extent; upon thefe, terminate a pair of large olfactory nerves, with the addition of a few branches from nerves refembling our fifth pair. In fome fishes, efpecially the haddock, the Doctor has obferved that the olfactory nerve, in its course from the head to the nose, paffes through a cineritious ball, refembling the cineritious matter connected to our olfactory nerve within the cranium. There can therefore be no doubt,' says he, that they enjoy the fenfe of fmelling; nay, there is great reafon to believe, that, fuited to their furrounding element, they are much more fenfible of odorous bodies diffolved in water, and applied by its medium, than we fhould be, if the application of the object was to be made to our organ of smell by the fame medium.'

The ftructure of the ear in fishes has been fo little examined till of late, that it has been a doubt whether they poffeffed organs appropriated to hearing. Swammerdam, in his Bibl. Natur. p. III. mentions a wonderful labyrinth of the ear in fifhes, but moft anatomifts fince his time have contented themselves with pointing out, as the organ of hearing, facs at the fides of the brain containing ftony fubftances, without pretending to fhew any external paffages leading to thefe facs, or the nerves or me dium by which they are connected with the brain of the animal.

As the defcription of the ear in fishes is new and accurate, we fhall endeavour to give an account of it as well as we can without the plates.

The organ of hearing is fituated at the lower end and pofterior fides of the cranium, feparated from the brain by membranes only. It confifts of three femicircular canals, viz. an anterior and a pofterior, perpendicular, and a middle horizontal one. Each perpendicular canal has a dilated portion or bulb at one of its ends, where it joins with the horizontal one; and in the anterior of those in a cod, a fmall fcabrous calcareous stone is lodged; the anterior end of the horizontal canal is likewife dilated. The fmall upper ends of the anterior and pofterior femicircular canals join together and form a common canal, which defcends perpendicularly. The horizontal femicircular canal has its large end joined to the bottom of the anterior canal, and its fmall end joins with the under end of the pofterior one, Thefe common canals open into the under part of the perpendicular canal, and of courfe meet there and communicate freely with that and with each other. We next find a fac of a confiderable fize, in which a large fcabrous calcareous ftone is lodged: this large ftone, as well as the fmall one mentioned above in the anterior canal, is furrounded with a viscous humour. A hole or opening in the fore or under part of the common perpendicular Canal leads into this fac in the fturgeon; but the Doctor could

discover

discover no fuch opening in the cod or the haddock. Very large nerves are fixed to the bulbous parts of the femicircular canals, and, fpreading out upon them, become fuddenly pellucid. On the fac which contains the large ftone, efpecially in the cod, a confiderable nerve is fpread in a moft elegant manner. The canals and fac contain, beflde the ftones, a vifcid humour; and as the femicircular canals are much småller than the cavity of the bone or cartilage which contains them, there is alfo, between their outer part and the bone or cartilage, a confiderable quantity of vifcid humour. In the cod, haddock, and the whole genus of gadus, a number of fmall fpheroidal bodies (which the Doctor has found to form part of the nervous fyftem) is obfervable within this cavity, floating in the vifcid humour, and fupported by small fibres of veffels and nerves. Several of the cartilagineous fishes, the raja, fqualus, &c. have a meatus auditorius externus, through which the found is conveyed by a watery vifcid liquor to the inner fides of the membranes of the femicircular canals and fac; but in the offeous fishes, and fome of the cartilagineous ones, Dr. M. has not been able to difcover any meatus auditorius externus; and is inclined to think that they really have not one, from the confideration, that the common canal or veftibule, where the three femicircular canals communicate, is separated from the cavity of the cranium by a thin membrane only; and that this cavity, in the greater number of fishes, contains a watery liquor in confiderable quantity; and that, by the thinness of the cranium, the tremor excited by a fonorous body may readily and eafily be tranfmitted through the cranium to the water within it, and fo to the ear.

The eye is next defcribed; in treating of which, the Doctor, after making fome curfory remarks on the coats, confiders the humours, their texture, fpecific gravity, shape, and powers of refraction.

Our Author concludes with the anatomy of two worms, namely, the Sepia loligo and the Echinus efculentus. The latter affords great opportunity for inveftigating the ftructure of abforbent veffels, and obferving how they perform their office. But it is totally impoffible to give any account of these two articles without the figures.

The numerous plates accompanying this work are most of them large folding fheets, which, though they are admirably adapted to illuftrate the fubject, are, on account of their coarfe nefs, by no means pleafing to an eye accuftomed to the elegance. of modern engravings.

R—m.

ART.

Art. I.

ART. XI.

FOREIGN LITERATURE.

OSITIONES PHYSICÆ, quas, annuo labore, in fcholis, &c. Propofitions in Phyfics, or a Syllabus of a Courfe of Lectures in Natural Philofophy, delivered by J. H. VAN SWINDEN, Profeffor of Philofophy, Mathematics, and Aftronomy, in the Academical School, Amfterdam; Member of feveral Literary and Philofophical Societies. Vol. I. 8vo. Hardewyk. 1786.

The ingenious Profeffor was induced to publish this laborious work, which he had drawn up for his own ufe, from having experienced the inconveniences arifing from the want of a text book in natural philofophy, in which each branch of this extenfive fcience is explained with fufficient minute nefs, and the late difcoveries inferted in their proper order with respect to the whole, fo as to constitute a regular and complete fyftem of phyfics. In most of the works now publifhed as elements of natural philofophy, the easier and more entertaining parts are copiously dif cuffed, but the more difficult, yet equally important, are scarcely attended to; and mathematical inveftigation, though effentially requifite in philofophical inquiries, is by many entirely neglected, or defignedly omitted.

Books of this kind, though not without their utility to perfons who have not time or opportunity to cultivate mathematical Audies, are by no means fufficient to form the philofopher. Experiment is indeed the ftandard by which every philofophical theory must be tried; but in many branches of phyfics, experiments will afford little inftruction to the fpectator, unless he be able to comprehend mathematical reafoning, and thus to difcern the reality of thofe principles, which experiments ferve only to confirm and elucidate.

Of the prefent work, only the first volume is yet published; but from the Author's plan, and this fpecimen of its execution, we are perfuaded that it will contain the heads of a very complete courfe of phyfics. It is preceded by two introductions; the one mathematical, containing a felection of theorems with which the ftudent ought to be well acquainted; and the other philofophical, relating to the study of phyfics in general, the objects and extent of this fcience, and the method and rules of philofophizing.

The fytem is divided into twelve books, of which, the first treats of the general properties of matter; the fecond, of the laws of motion, the third, of ftatics and mechanics; the fourth, of hydrostatics; the fifth, of mathematical dynamics, or the laws according to which folid bodies act upon each other by percufLion and collifion; the fixth, of hydronamics, or hydraulics.

Thefe

Thefe fix books contain the elements of general phyfics, which relate to the properties of matter, and are founded chiefly on mathematical principles. From these our Author proceeds to particulars, and in the feventh book treats of air, and aeriform fluids; in the eighth, of fire and electricity; in the ninth, of light; in the tenth, of phyfical dynamics. Under this laft head, he confiders the various kinds of attraction, the cohefion and elafticity of different bodies, and the powers of the magnet, &c. In the eleventh book he inquires into the elements of bodies, and in the twelfth, concludes his courfe with meteorology, which, he obferves, is the moft difficult branch of phyfics, and cannot be explained, or even comprehended by the ftudent, till he is well verfed in the fubjects of the preceding books.

The Profeffor has diftributed his propofitions into three claffes, diftinguished by the fize of the letter in which they are printed. The first clafs comprehends thofe principles, which are neceffary to all who would acquire a clear and well-founded knowledge of natural philofophy; thefe conftitute the text of his public lectures. The fecond contains propofitions of a more difficult kind, calculated only for those who wish to cultivate a more particular acquaintance with phyfics. The third clafs confifts of fuch as are propofed for the further investigation of perfons who have made a confiderable progress in these ftudies. This and the fecond clafs are defigned only for private lectures.

After each propofition, the Profeffor refers to thofe authors by whom it is demonftrated and explained; and thefe references are the more valuable, as they extend to the best papers concerning phyfics that have been published in periodical works, and in the Transactions of moft of the focieties and academies of Europe; fo that this work may ferve as a general philofophical index, or common-place book: from the propofitions themselves, the reader may learn the principles which have been established, and, by the references annexed, he is directed to thofe writers by whom they have been proved and illuftrated.

Such is the plan and defign of this laborious work; which, though not calculated for the many, may be highly ufeful to academical ftudents, and to those whofe office it is to inftru&t youth in this noble science.

Art. 2. Erfarunghen von innem, &c. i. e. Obfervations on the interior and exterior Structure of Mountains. By Fr. M. H. DE TREBRA. Folio. 244 pages, and 8 coloured Plates. Deffau and Leipzig. 1785.-This work is fplendid and instructive. It contains a great variety of excellent obfervations, relative to a branch of natural hiftory, which is yet, perhaps, but in the dawn of its progress toward perfection.

Art. 3. Anfangs-Gründe der, &c. i. e. Elements of Chemistry, confidered in its Relation and Application to the ufeful Arts. By

M. G.