THE

MONTHLY REVIEW,

For SEPTEMBER, 1794.

ART. I. Zoonomia; or the Laws of Organic Life. Vol. I. By Erafmus Darwin, M. D. F. R. S. Author of the Botanic Garden. 4to. pp. 586. 11. 55. Boards. Johnfon. 1794.

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N few things do men of reading and inquiry differ more than in the manner in which they are affected toward a new fyftem. While fome perufe with avidity every promifing attempt to establish a general theory of a science in which they are interested, enter into it with ardour, and feel great pleasure in following all the mazes of plausible and ingenious fpeculation, even if, on the whole, they cannot admit its truth; others, on the contrary,-more impreffed with the experience of former failures, than fanguine in their expectations of new fuccefs, aware of all the numerous inlets to mistake and delufion, and dreading the interference of fancy when truth alone is the object,-receive with coldness every effort which promises more than they expect to fee realized, and are perfectly contented to poftpone their examination till the public voice has given confequence and authority to the attempt.

It is probable that the reception of the work before us will greatly depend on the proportion of the above two claffes among those who pay attention to its fubject. Its author is well known as an ingenious philofopher, of extenfive knowlege and large inquiry; he is also equally known as a poet, diftinguished beyond most of his contemporaries by the boldness of his imagination; and his characters of poet and philofopher have been fingularly blended in the fame performance. It is easy, therefore, to judge what will be the various impreffions on different minds on the appearance of a work under his name, which promises an endeavour of vast extent and moment, to reduce the facts relating to animal life into claffes, orders, genera and fpecies; and, by comparing them with each other, to unravel the theory of difeafes. With refpect to ourselves, we would, as much as poffible, keep down all prepoffeffions on the occaVOL. XV. B

fion;

fion; and we conceive that we shall beft perform our duty to the author and the public by proceeding immediately to an analytical view of the whole performance, leaving our readers afterward to determine how far its facts and reafonings in the detail may be worthy of their attention.

After a fhort preface, in which we are acquainted that the greatest part of the work has lain by the writer during twenty years, he commences with

SECT. I. Of MOTION. The motions of matter are arranged under three claffes; thofe belonging to gravitation, to chemistry, and to life. The latter, comprehending all animal and vegetable motions, are the fubject of this work.

S. 2. EXPLANATIONS and DEFINITIONS. This fection begins with a general view of the animal economy; of which the moft remarkable opinion is, that the immediate organs of fenfe probably confift of moving fibrils, having a power of contraction like that of mufcles. Senforium is ufed to fignify not only all fentient parts, but the living principle refiding throughout the body. By idea is meant thofe notions of external things with which the organs of fenfe bring us acquainted, and it is defined to be a contraction, or motion, or configuration, of the fibres of thofe organs. Senfual motion is used as fynonymous. with it. Perception includes both the action of the organ, and our attention to it. Senfation is ufed to exprefs pleasure or pain in its active state alone. Ideas of recollection are thofe voluntarily recalled-thofe of fuggeftion come from habit. Affociation is a fociety of things in fome refpect fimilar, and does not include the connection of cause and effect. All the definitions of this fection are afterward more particularly explained.

The bufinefs of the 3d fection is to fhew, by experiment, that the organs of fenfe poffefs a power of motion, and that these motions conftitute our ideas; also that ideas of the imagination confift in a renewal of these motions. The first experiments adduced to this purpose relate to optical spectra. One of the affertions moft worthy of accurate investigation in this fection is, that, when an organ of fenfe is totally destroyed, the ideas which were received by that organ perifh with it. This, indeed, ought to follow from the writer's hypothefis, and he gives fome inftances of the fact: but we are scarcely. prepared to receive it as a general truth.

S. 4. lays down the laws of animal caufation, afterward to be exemplified.

S. 5. enumerates the four faculties or motions of the fenforium, irritation, fenfation, volition, and affociation. They are thus defined: Irritation is an exertion or change of fome extreme part of the fenforium refiding in the muscles or organs of

fense,

fenfe, in confequence of the appulfes of external bodies. Senfation is an exertion or change of the central parts of the fenforium, or of the whole of it, beginning at some of the extreme parts. Volition is an exertion or change of the central parts, terminating in the extreme parts. Affociation is an exertion or change of fome extreme part of the fenforium, in confequence of fome antecedent or attendant fibrous contractions. The above faculties are alfo called fenforial motions.

S.6. defcribes four claffes of fibrous motions, which are contractions of the fibrous parts, correspondent with and caused by the four fenforial motions above-mentioned. They are in confequence denominated irritative, fenfitive, voluntary, and afficiate fibrous motions.

S. 7. treats of irritative motions, noticing the different modes in which they are excited, the modifications that they undergo, and the affociation of other motions with those brought on by the primary irritation. It is alfo obferved that irritative ideas often exift without our attention to them; as when, though loft in thought, we avoid a tree or bench that stands in the way of our walk.

S. 8. concerning fenfitive motions, obferves that they were originally excited by irritation, are occafionally obedient to volition, and have other motions affociated with them.

S. 9. on voluntary motions, ftates them to have been originally excited by irritations. Ideas of recollection are a class of these voluntary motions, on which Reason, or the act of comparing different ideas, depends. Voluntary motions are occafionally caufable by fenfations, made obedient to irritations, and affo ciated with other motions.

S. 10. is on affeciate motions. Mufcular, fenfitive, and voluntary motions and ideas, excited in trains or tribes, become afsociated, and have ever after a tendency to arise simultaneously, or in fucceffion.

Some additional obfervations on the fenforial powers, in fec. 11. relate to the various kinds of ftimulation, as adapted to different parts; to fenfation and volition, defire and averfion, voluntary actions and affociations. It is afferted that the activity of the power of volition produces the great difference between men and brutes.

S. 12. treats of stimulus, fenforial exertion, and fibrous contraction. The latter is firft confidered. In order to bring the particles of a mufcular fibre to that nearer approximation in which its cnotraction confifts, fome other agent is neceffary, which is the fpirit of animation or fenforial power. After animal fibres have for fome time been excited into contraction, a relaxation fucceeds, even though the exciting cause continues

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continues to act. This appears to be owing to an expenditure or diminution of the spirit of animation previously resident in the fibres. It is fucceeded, after a certain interval, by a new contraction, and this interval is lefs in weak than in ftrong fubjects; which accounts for the quick pulfe in fevers with debility: yet the contraction itself is performed with more velocity in ftrong than in weak fubjects. After a fibre has been excited to contraction, and the cenforial power ceases to act, the last fituation or configuration of it continues, unless difturbed by fome extraneous caufe. A contraction somewhat greater than ufual produces pleasure; one still greater produces pain. As, in every contraction of a fibre, there is an expenditure of the spirit of animation, increased action diminishes the propensity to activity; on the contrary, lefs fibrous contraction than ufual caufes an accumulation of the spirit of animation, and increased propenfity to activity. Hence the capability of being excited to action is perpetually fluctuating. When much and permanently above or below the natural ftandard, it becomes a disease. In fenforial exertion, three things are to be obferved; the ftimulus, the fenforial power, and the contractile fibre. An external ftimulus firft brings into action the faculty called irritation, which caufes contraction of the fibres, and this, if perceived, produces pleasure or pain; this is another ftimulus capable of caufing contraction by the fenforial faculty termed fenfation; or it introduces defire or averfion, which excites another faculty termed volition, which may act as another ftimulus; and, in conjunction with all these, the other fenforial faculty, termed affociation, may be called into action. The word ftimulus may therefore be properly applied to any of the above four caufes exciting the four fenforial powers into exertion; and the quantity of motion produced in any part of the fyftem will be as the quantity of ftimulus and the quantity of fenforial power refiding in the fibres. Where thefe are great, ftrength is produced; where deficient, weakness. If, the quantity of fenforial power remaining the fame, that of ftimulus be leffened, a weakness of contractions enfues, which may be termed debility from defect of flimulus; if, the quantity of ftimulus remaining the fame, that of fenforial power be leffened, debility from defect of fenforial power is the confequence. The former is the direct debility of Dr. Brown; the latter, the indirect. On thefe principles, with that of the exhauftion of the ípirit of animation by fibrous contractions, and its renovation and accumulation on quiefcence, the phenomena of fevers, and various other corporeal affections, are developed. Some remarks relative to medical practice close this fection, which are either derived from the above theory, or, at least, are

made

made happily to coincide with it. From thefe, we shall copy what the writer terms two golden rules refpecting the application of stimuli. In fevers with debility, when wine or beer are exhibited, if the pulfe becomes flower, the stimulus is of a proper quantity, and fhould be repeated every two or three hours, or when the pulfe has again become quicker. In chronical debility brought on by hard drinking, the patient should be directed to omit a fourth part of his accuftomed quantity of vinous fpirit. If, in a fortnight's time, his appetite increases, be fhould omit another fourth part: but, if this farther diminution impairs the appetite, he should remain where he is. At the fame time, fleth-meat is recommended, with Peruvian bark and steel in fmall quantities between meals, and opium with rhubarb at night.

S. 13. relates to vegetable animation. Some of the well-known facts refpecting the irritability of plants are here mentioned. Their fecretions are compared to thofe of animals; and the individuality of every bud on a tree is afferted. Next, the marks of fenfibility fhewn by the fexual parts of plants are recited, and the writer does not fcruple to afcribe the paffion of love to piftils and anthers; thus feriously maintaining, as a philofopher, opinions which we conceived to be the fport of a poetic imagination in his beautiful work entitled The Loves of the Plants. He touches on the curious inquiry whether vegetables have ideas of external things? which, from arguments that feem to prove them poffeffed of a common fenforium, he is inclined to anfwer in the affirmative.

S. 14. on the production of ideas, goes over the several organs of the fenfes, and the manner in which objects affect them: but, in fo very concife a difcuffion, we cannot expect much new elucidation of points which, fingly, have cost much labour to many philofophers. Befides the ufual enumeration of fenfes, he adds the fenfes or appetites of hunger, thirft, heat, extenfion, the want of fresh air, animal love, and the fuckling of children.

The 15th fection, on the classes of ideas, is purely metaphyfical, and offers nothing new to the informed reader.

S. 16. on infine, is very curious and entertaining, but will probably by many be thought fanciful and inconclufive. Its general purpose is to fhew that the blind impulfe in animals, to actions the reafon and confequences of which are not feen, (which we ufually call inftinét,) does not in reality exist,-but that early unmarked affociations or previous experience have been the true causes of those actions. He traces thefe affociations and acquirements in the early motions, fenfations, and aftes, of animals. Thus, our fenfe of beauty he derives from