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Haller charges him with making the foul divifible. Dr. Whytt admits, alfo, contrary to experiments, the Stahlian doctrine of univerfal fenfation*; a doctrine clearly difproved, by the effect of ligatures, or divifion of nerves, in the living animal. While he combats the vis infita, he produces fome facts which contradict his own theory of the involuntary motions, and feem to fhew, that the motions of thofe organs may be explained from the ftimulus of the contained fluids. Thus, the power of ftimuli applied to any muscular part, even to a voluntary muscle, is greater than the power of the will over that part†, and the peristaltic motion of the inteftines fometimes continues, after the action of the heart has ceafed, from the ftimulus of their contents. And Dr. Whytt is obliged to confefs, that the mind has no concern, as a rational agent, with the coalefcence of the ductus arteriofus & ductus venofus after birth§; for the mind is not even conscious that such parts have ever existed, and their circumstances are only known by anatomical investigation.

Dr. Monro explains his opinion of the intellectus agens, in the human body, in thefe few

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I. Ib. p. 192. Dr. Haller fays, Vox (vis vitalis) non perinde placet, cum vis noftra vita aliquantum fupervivat. Phyfiolog. T. IV. p. 464.

VOL. III.

Vit. and Inv. Mot. p. 169.

words

words;

"that the power which created all things, "which gave life to animals, and motion to the "heavenly bodies, continues to act upon, and to "maintain all, by the unceafing influence of a

living principle pervading the universe, the "nature of which our faculties are incapable of " duly comprehending." But this theory seems liable to the fame objection with the notion of a plastic power; that neither of them affords a fatisfactory explanation of the phenomena of sense and motion. For the plastic power, or living principle, must be either material or immaterial: if it be material, then it must be allowed that matter, `as matter, is fufceptible of life; now as the existence of the plaftic power is merely affumed, we have a right, in this cafe, to fuppofe that the body acquires vitality by a certain degree of organization, as a preferable hypothefis. But if the plastic power be declared immaterial, its action on matter is as difficult to be conceived, as the action of an immaterial mind on the body, and confequently nothing is gained but a term by the fuppofition. If the living power be supposed to be an immediate act of the Deity, an opinion which has been held by many philofophers, this is liable to ftill ftronger ob

*Conclufion of Obf. on the Nervous System.

+ Sennert. Epitom. Phyf. p. 82. P. 530.

Alfted. Encyclop.

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jections; for the confequence would be, as it is urged by one of Cicero's fpeakers, cum miferi animi effent, quod plerifque contigerit, tum Dei partem effe miferam, quod fieri non poteft*. If it be faid that the living principle, on this hypothefis, is the connecting medium between the mind and the body, this fuppofes the Deity to act fubordinately to the human mind, which cannot be admitted.

When Mr. Hunter's doctrine of the life of the blood was first propofed, it was faid to be a revival of an opinion fuggefted by Dr. Harvey †. A very fimilar theory, however, prevailed long before Dr. Harvey: Galen made the heart the feat of the calidum innatum, and Sennertus exprefsly fays, that the heart and arteries form and contain the vital power. Since the time of Dr. Harvey, the life of the blood has been afferted by several authors of eminence. Willis fays, Sanguinis animationem, non folum placita philofophorum, fed indubitata facra fcripturæ teftimonia plané afferunt §. Hoffman employs the fame argument to prove the fame affertion, and he elsewhere expressly

* De Nat. Deor.

+ Medical Comment. vol. II. p. 198.

Inftit. Med. p. 338. Nothing could have prevented this able writer from attributing life to the blood itself, but his belief in the common perfuafion, that the right ventricle of the heart contained air alone.

De Mot Mufc. p. 71.
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mentions that the blood contains the vital principle* The fame opinion may be found in tical authors, particularly in Huxham,† who even mentions the red globules as the peculiar feat of life.

Mr. Hunter is faid "to confider a muscle cut "out of the body to be alive as long as it con"tinues capable of being acted upon by ftimuli "of any kind ;" and to be of opinion, << that "the particular parts of an animal body have a "principle of life, independent of the effect "which arifes from their union as one fyftem." The proof of these propofitions, it will be readily feen, is included in that of the particular doctrine they are advanced to fupport.

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Mr. Hunter" alledges that, in the nature of things, there is not a more intimate connection "between life and a folid, than between life and "a fluid §;" this argument is inconclufive; for we cannot, a priori, ascertain the degree or fpecies of organization requifite to a vital part.

Mr. Hunter's first direct proof of the life of the blood is, that it unites living parts when effufed between them. That living parts unite, in fome cafes, in confequence of mutual con

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ta, is certain; but it is by no means certain that this union is effected by an interpofed fluid*, because the phænomenon admits of a more probable explanation, which comes under the next obfervation.

The second direct proof of the life of the blood † is, that the blood becomes vascular, like other living parts: and " Mr. Hunter has a preparation, "in which he thinks he can demonftrate veffels "rifing from the centre of what had been a "coagulum of blood, and opening into the "stream of the circulating blood ‡." That fuch an effort should take place, in the centre of an effused fluid, not affected by external impulfe, iş inconceivable, except on the fuppofition that the blood is a rational as well as a living fluid, and poffeffed of mufcular fibres, or fome fimilar organs. And granting the blood to be rational, it is much more likely that the first attempt towards a reunion of feparated parts fhould be made at the orifices of the divided veffels where the operation would be eafieft, than in the centre of the fluid effused between them; that is, there will be an elongation of the divided veffels. And that this does actually take place, appears from Dr. Mon

It is well known that if the oppofite branches of two healthy trees be tied together, they will coalefce, although no incifion had been made in either, nor any part of their bark removed.

+ Ib.

P. 200.

↑ Id. Ib.

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