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cury, the mercury, after having produced its ufual effects, has paffed through the skin in a metallic form, and has amalgamated itself with watches, and the gold in the pocket, &c. The oxyd of mercury, in paffing through" the human body, parts with its oXYGEN, and it is this oxygen alone, which remains combined with the fyftem, that the effect produced by oxydated mercury is ow-` ing. Thus arsenic, under its metallic form, has no effect upon animals; but the white oxyd of this metal is one of the most terrible poifons; for it hyper-oxygenates the organized fibre with which it comes into contact, and reaffumes its metallic form.

The cause of the beneficial effects of feel on the animal œconomy has not been hitherto fufficiently fcrutinized. According to Monf. CHAPTAL, the red particles of blood almost wholly confift of iron. And it is well known that the blood acquires its florid colour from its exposure to the air in the vesicles of the lungs, from whence nothing but VITAL AIR is abforbed. It seems therefore probable, that the red particles of blood confift chiefly of particles of iron, calcined by the OXYGEN, or VITAL AIR, and reduced to the state of a red oxyd of iron. Hence it appears, that chalybeates will not only

VOL. I.

increase

increase the quantity of red particles in the blood on which the ftimulant and tonic powers of that fluid, most probably in a great measure depend, but will enable it to decompose a larger quantity of air which is received in the lungs by respiration, and thus occafion a greater evolution of heat, and will produce the fame effect upon the system, as if a much purer atmosphere had been breathed for fome time *.

By various experiments of Dr. HALE's, compared with those of Dr. INGENHOUZ, it is evident, fays the celebrated author of the Guide to Health, that vegetables in fummer, while they enjoy the fun, are inceffantly decompofing water, and emitting from their leaves their oxygen combined with caloric in the form of VITAL air. And it is clear, that as long as water is fupplied abundantly, they not only preferve their vigour, even at miday with the most fervent heat, as in the fouth of Spain, but make a rapid progress in their growth, and emit a proportionable quantity of vital air. May we not infer from thence, that their irritability depends on OXYGEN, and their vital energy on a plentiful supply of this reviving ele

* Dr. GARNETT.

ment,

ment, whilft the hydrogen of the water not only fupplies the combuftible part of vegetables, but, by depofiting its caloric, maintains the vital heat.

Should Drs. GAHAGEN and THORNTON purfue the experiments they have fo fuccessfully begun, or should other philofophers, with the fame ardour of enquiry, take up this fubject, we fhall then be able, fays the Rev. Mr. TOWNSEND, to afcertain a fact, afferted by the former, that the plants called fenfitive may be deprived of their fenfibility by opium, alkohol, and oil; whilst vinegar, and the oxyds of arfenic or mercury, communicates even irritability to plants as did not poffefs it before.

Were these facts well afcertained, it would throw great light upon the operation of these medicines in the human frame, and contribute to establish the system, now received by many, refpecting irritability as induced by OXYGEN.

2."Whatever diminishes the quantity of OXYGEN in organized bodies, diminishes at the fame time their irritability."

A fmall quantity of azotic air was injected into the jugular vein of a dog. The animal died in twenty feconds. Upon opening the thorax, the pericardium, and the heart,—the right auricle and ventricle were filled with black blood. The left ventricle was of its ordinary colour.

colour. The heart, and almost all the muscles, had loft their irritability almost entirely; they contracted but weakly upon the application of the strongest stimuli, fuch as fulphuric æther, and the electric spark.

When confumptive patients under the judicious management of Dr. BEDDOES, at the Hot-Wells, Bristol, and Dr. THORNTON in London, breathe azotic or hydrogen air, blended with a fmall portion of vital air, the circulation, irritability, fenfibility, and appetite is diminished, and the hectic fever is abated *.

There was long fince a difpute between Dr. WHYTT and Baron de HALLER refpecting irritability, and that dispute is not yet completely settled. The former attributed this power wholly to the nerves; the latter to the mufcular fibre, independent of the nerves.

But were we permitted to reason from analogy, we might fufpect, if not conclude, that fince plants, by irritability alone, without brain or nerves, exercise the vital functions; thefe likewife may in animals depend on the irritability of the mufcular fibre, whilst fenfation,

* Vide Obfervations on the Medicinal Use of the Factitious Airs, by Dr. BEDDOES; alfo the Letters of Dr. THORNTON, Dr. EWART, Dr. PARRT, &c. to the fame.

thought,

thought, and voluntary motion, refult undoubtedly from the presence of a brain.

The womb, in the time of pregnancy, increases in substance and fize probably fifty times beyond what it naturally is, and this increase is made up of living animal matter, which is capable of action within itself. I think we may fuppofe its action more than double; for the action of every individual part of this vifcus, at this period, is much increased, even beyond its increase of fize; and yet we find that the nerves of this part are not in the fmallest degree increafed. This fhews that the nerves and brain have nothing to do with the actions of a part: while the veffels, whofe ufes are evident, increase in proportion to the increased size: if the fame had taken place with the nerves, we fhould have rea foned from analogy!

If nerves, either of themselves, or from their connec tion with the brain, gave vitality to our folids, how fhould a folid continue irritable, after a nerve is destroyed, or paralytic? for the part continues to be nourished, although not to the full health of voluntary action; and this nourishment is the blood, for deprive it of the blood, and it mortifies.

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