That Light, if nothing hinders, gives motion to bodies, in the direction of its rays; but if it cannot in this direction, it gives motion in any other direction the neareft to it, where it meets with leaft refiftance."

A Treatise on the three different Digeftions, and Difcharges of the Human Body; and the Difeafes of their principal Organs.

By Edward Barry, M. D. F. R. S. Profeffor of Phyfic in the University of Dublin, and Physician-General to his Majefty's Ariny in Ireland. 8vo. 6s. Millar.

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HIS excellent medical performance bears all the marks of the Author's ability and experience in his profeffion. It was the refult, as the preface informs us, of his frequent reflection on the Difeales of the Lungs, and the Nature of Nutrition; on which he had published a treatise above thirty years paft, which his prefent maturer judgment modeftly reprefents to him as an imperfect and too early performance. We find then his further confideration of Pulmonary Confumptions has led him into a profound and retrospective inveftigation of that defective ftate of all thofe Digeftions and Discharges of the body, which may, more or lefs, difpofe to that, and to fuch other chronical difeafes, as are the particular fubjects of the present treatise.

As it would be extremely difficult to make a useful abftract of a work, into which the Author has crowded, as we may fay, great medical knowlege and literature, in a manner more clofe and appofite, than oftentatious; and as the entire treatise [which, he juftly obferves, it was more difficult to contract into the limits he had prefcribed it, than it would have been to have enlarged it] deferves the strict confideration of every young Regular and may ufefully entertain even thofe more advanced, especially on the Diseases of the Lungs; we shall therefore chiefly attempt to give a general view of the order and connection of fome of his chapters, with their different fections; inferting a few of many fuch paffages as. appear to us new, and more properly Dr. Barry's own fentiments and fuggeftions, which will at the fame time exhibit his manner of reasoning, and of writing.

The first chapter treats of the First Digeftion; as it was neceflary to give fome notion of its compleat and falutary ftate, in order to a better conception of its morbid or defective one This falutary state of Digeftion is very clearly dif

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played here, to any who have attentively furveyed the ftomach, and its fituation amidst the contiguous and adjacent Vifcera. But as this Gentleman, with all his liberal regard to reputable medical Writers, is actuated by a greater deference to Fact and Reason than to Authorities; after obferving the calculations of Pitcairn, (on Borelli's Principles) of the force of the ftomach, which he juftly calls wild computations; and making a practical diftinction between the abfolute force which a Mufcle can exert, and that real force which it ufually does, he rationally adds, page 18, speaking of the ftomach: For its powers are much weaker than they < are generally supposed to be, and not capable of diffolving the folid parts of animal or vegetable bodies; but only of attenuating, and expreffing the fluid parts. This is confirmed by repeated and obvious experiments; for Currants, Grapes, or any or any other Fruit, or Seed, fwallowed whole, and entire, remain fo in the excrement.

Hence the reafon plainly appears, why the ftomach is not diffolved by its own action; of which it must certainly have ⚫ been in great danger, if it contained an active ferment, or could excite fuch a powerful attrition, as might be capable of diffolving, or grinding the folid parts of fuch food, as are often received into it, and which have as strong a cohesion as the ftomach itself.'

In mentioning the Peristaltic Motion of the Inteftines, as a confiderable inftrument in a further elaboration of the first Digeftion, he thus ingeniously fuggefts the analogy between this motion and that of the Heart; and the true, or moft probable, Reafon we have met with, why the Lacteals have never as yet been injected.

Is not this muscular action alternately relaxed, and contracted, somewhat analogous to that of the Heart? and is not the power of Abforption alone, infufficient to receive and propel the Chyle through the Lacteals, whose motion acquires no immediate influence from that of the Heart? On which account, this defect is not only supplied in their origin, but through their whole courfe, by a various and exquifite mufcular motion.

Hence appears the reason, why the Lacteals could never by any art be injected in dead bodies? Their oblique fituation, and minutenefs, requiring this peculiar motion, to overcome their refiftance.-Van Helmont, therefore, might with more justice, have placed his Archæus there, than in

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the Pylorus, which he confidered as a careful Centinel, ''that denied a passage to any thing injurious to life.”,,

Having represented the extraordinary proportion of Nerves fent to the Stomach and Inteftines, which are more large and numerous than feem neceffary for their mufcular motion; and after noting, especially, their uncommon proportion and diftribution throughout the Mesentery, he makes the following curious fuggeftion.

It is therefore more than probable, that the Chyle in its paffage through the Mefentery, is impregnated with a great quantity of Animal Spirits."'

Finally, under this article of the first Digeftion, Dr. Barry fuggefts the reason, why perfons of the strongest constitution are most apt to be coftive; fuppofing, in fuch, the finer part of the Faces to be admitted into the abforbent Veins of the great Inteftines, which, he imagines, like fo many volatile. Spirits, raised by diftillation from putrefcent animal bodies, greatly to contribute to animate the whole machine.'-This abforption of part of the Faces into the blood feems, at first fight, to give us fome notion of the mafs becoming more impure and feculent from it; upon which opinion we find clyfters often directed in the beginning of acute difeafes, to cleanse and empty the inteftinal canal: and, indeed, our Author himself fuppofes, page 105, the retention of the Excretions, all of which,' he obferves, are of the putrefcent kind, to be a powerful and frequent caufe of pu⚫trefaction in animal fluids.' And here by the way we may query, whether the difagreeable odour of the Perfpiration in fome vigorous perfons, efpecially after much labour or exercife; and even the Fætor of the breath in others, (whofe Lungs are found) may not, in part, refult from a vaporous difcharge of fuch feculent particles from the circulation, into which they were abforbed in a groffer confiftence? Be this however as it may, the admiffion of it will not invalidate our Author's inference on this point; as thofe feculent particles may be innoxious, and even ufeful, in a healthy ftate, which would aggravate a disease, and particularly a putrid one. For as the ftimulation from the contents of the blood, in its natural crafis, has been confidered by excellent Phyfiologifts, as one cause of its circulation through the Heart; an unusual defect of its ftimulating principles would very probably conduce to its feebler motion, and the diforders refulting from fuch defect. On a caufe very fimilar to this Dr. Barry establishes the reafon, p. 33, 34, why perfons of a low nervous constitution, are generally fo much depreffed by the lightest Purgatives:

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and why that depreffion is, in a great meafure, prevented, or removed, by the ufe of Afa Fortida and volatile Medicines." These facts occurring, not rarely, in practice, reflect no inconfiderable light on this hypothefis, which, however doubtful to fome, may prove the leaft indigeftible to those who shall reflect the most upon it.-The only fection annexed to this chapter, of the First Digeftion, treats of a Depraved Appetite and Indigeftion; and contains many judicious remarks, inferences, and directions, recommending a few fuch medicines as seem indicated from a very rational confideration of its different causes,

The fecond chapter is appropriated to the Second Digestion, or the Commutation of the Chyle into fuch a fine Serum, as is qualified to pervade the finest veffels of the body. Our Author confiders the Lungs as the principal organ of this operation, and very practically remarks here, That as all the new Chyle muft pafs the Lungs, before it is tranfmitted into the general arterial fyftem, Medicines will arrive to the Lungs with their virtues and qualities more un♦ altered, than to any other more diftant bowels, to which they must be diftributed through the arterial fystem, in 'much lefs quantities, and more changed.' The only fection annexed to this chapter, treats of the Tenacity of the Blood; in which the Author judiciously diftinguishes that Tenacity, which it receives through too intense a motion and heat, from that vifcid texture arifing from too languid a circulation, whence the globules are more light and diffolved, and their cohefion weaker. He obferves the great error in practice, of attempting to remove the firft by ftimulating volatile medicines and blifters, which, he thinks, must increase its tenacity, by increasing its heat and motion; and directs a rational procedure in this tenacity, as well as in this vifcidity, of the blood,

The third chapter treats of Urine, and the Difeafes of this fecond Difcharge. He confiders this fluid as the fuperfluous or excrementitious parts of the Chyle, after its elaboration into Serum; and in the immediately fubfequent fections, of the Nature and Formation of Calculous Concretions, he oppofes the opinion of their being formed from tartareous or acid falts; truly affirming, that they are of a contrary nature, confifting of terreftrial, oily, and alkaline parts, [which has appeared from experiments] and adding, that their hardness will always be proportioned to the denfity of the oily, and the minutenefs of the terreftrial parts. The force of Lithontriptic Medicines, he obferyes, muft confift in attenuating

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and changing their oil, their cement, which both acid and alkaline medicines, as Spirit of Nitre and of Salt, and Limewater, are qualified to effect. The fecond fection on this topic,-Of the Defects of the Second Difcharge-is chiefly employed in relating a remarkable and fatal fuppreffion of urine, which fell under Dr. Barry's immediate cognizance and treatment; and the third fection-Of a Diabetes-diftinguishes it into the four different causes from which it may flow, fuggefting remedies fuitable to each.

The fourth chapter-Of the Nature of Aliments, animal, and vegetable-is truly rational and ingenious. He premises in it, that, from the preceding accounts of the first and fecond Digeftions, and of the Excretions peculiar to them, it is evident, that the Prefervation of Health in different. conftitutions, and the Cure of many Difeafes, will principally depend upon a Regimen of Diet suited to them;" as he concludes it by obferving, very juftly, that if this material part in the Art of Healing is neglected, the moft powerful medicines will be often ineffectual.' Our learned Profeffor here encounters Dr. Cheyne's almoft fundamental principle" That a Vegetable Diet is the moft proper Regi"men for Valetudinarians, and the most effectual means of "removing their complaints,"-which principle our Author, not improbably, imagines, Dr. Cheyne to have laid down, from finding fuch a diet agree with himself, and his own cafe'-but which inference of that Phyfician's was erroneous, if his conftitution was naturally robuft, as our Author fuppofes, and we have always conceived, it was, from feveral anecdotes of his extraordinary appetite, fize, &c. Indeed, it fhould feem as if Dr. Cheyne attended here, folely or principally, to their more eafy reduction in the ftomach, (the first Digestion) from the flighter cohesion of their fibres : but Dr. Barry, not refting here, confiders the greater difficulty of affimilating the Chyle, from fuch acefcent food, into a proper human Serum by the fecond Digeftion, in Valetudinarians; as he denies any manifeft acidity in the Blood, or any of the animal humours; but rather a difpofition in them to an alcalefcence; whence the strongest Digestions will be most equal to a fufficient and falutary affimilation of fuch vegetable juices. Our Author, however, excepts Milk in this cafe, as neither entirely vegetable nor animal; and which, he thinks, already fo far prepared, as to be eafily affimilated into Serum; and to retain so much of an acefcent nature, as is fufficient to prevent that difpofition, which all animal fluids. have, to putrefaction. Neither is our Author's diffention from

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Dr.