der that Dr Hale should have been deterred from their repetition, by their excessive barbarity; and besides, from the experience and character of sir E. Home in this kind of investigation, they can be relied upon with as much confidence, as any single series of experiments ever can be.

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The question then to be determined is, whether, having once got the fluids in this summary way into the circulation, they may not in the ordinary course of the functions be found in the bladder after the short period of time in which this is known to take place, without the necessity of supposing any more direct passage. The object of Dr Hale is to show that they may, and in this we conceive he has perfectly succeeded. With this view it was first necessary to ascertain what length of time it would require, for fluids to be carried from the stomach to the bladder, through the medium of the circulation. This can never be ascertained with any degree of precision; yet some approach to the knowledge desired may be made by estimating the rapidity and force of the blood in circulation.' p. 39. Supposing the whole quantity of blood in the body to be thirty pounds, and that thrown out at each contraction of the ventricle, which happens at least seventy times in a minute, to be two ounces; the complete circulation of any one definite portion of blood would be accomplished, according to Dr Hale, in three minutes and twenty-five seconds; and calculating the quantity thrown out at each contraction at only one ounce and a half, the period would be only extended to five minutes and one second. Now, 'the distance from the stomach to the kidneys, through the circulation, is that from the stomach to the heart, through the lungs, back to the left side of the heart, and from the mouth of the aorta to the mouth of the emulgent arteries. This at the most, cannot be supposed to exceed one half of an entire revolution; and is probably less than one fourth. The time requisite, therefore, as far as the circulation is concerned, for fluids to pass from the stomach to the kidneys, is not more than from two to three and a half minutes, leaving the remainder of the time which actually intervenes between their being taken in drink, and ejected in urine for their absorption in the stomach, and their secretion and excretion in the kidneys and bladder.' pp. 40, 41.

This calculation, which is certainly within bounds, shows sufficiently that there is nothing at all improbable in supposing

the passage of fluids to be effected through the circulation and kidneys. And this being the natural course, the burden of proof clearly lies upon the other side; and had no question ever existed upon the subject, no further investigation would have been esteemed necessary. Dr Hale has, however, by a few well designed experiments, added new certainty to these conclusions. It is unnecessary to enter into any detail of these experiments; the results to which they lead we shall state in his own words.

1. The speedy discharge of watery urine after taking a large quantity of liquid in drink, is not occasioned by sympathetic excitement of the urinary organs, but by the actual excretion of the fluid received.

2. The same portions of fluid, which are received into the stomach, begin, under certain circumstances at least, to be collected in the bladder within twenty minutes from the time when they are taken.

3. When a large quantity of fluid is taken, the excretion of urine is greatly increased; but the increase does not bear any very exact proportion to the quantity of drink. The increased discharge begins in about twenty minutes, is at its height in about an hour, and terminates, generally, in less than two hours.

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4. When a liquid, which is colored with rhubarb, is taken, the color of the rhubarb appears in the urine; and its appearance that excretion is not at all confined to the time of the increased discharge, which is occasioned by the quantity of fluids received. 5. When a liquid, which is of such a nature as to admit of ready detection in the animal fluids, is taken into the stomach, if the quantity is sufficiently large to affect the whole mass of blood, it will be found in the blood drawn from the veins, as soon as in the urine; although it will continue to appear in the urine after it has disappeared from the blood.

6. When a quantity of coloring matter, sufficient to affect the whole mass of blood is taken, mixed with a large quantity of liquid, the color appears in the urine, as soon, at least, as the excretion begins to be increased, and is at the deepest before the increase of urine is at its height; but if the quantity of coloring matter be only a little more than sufficient to tinge the amount of liquids taken, it does not appear in the urine until after a considerable quantity of watery urine has been passed, and does not give its deepest color until some time after the excretion has diminished. pp. 56-58.

7. The rapidity, with which fluids pass from the stomach to the bladder, is not increased by increasing their quantity.'

8. It results from the whole, that the only mode by which

fluids received into the stomach can pass into the bladder, is by absorption into the blood, and subsequent secretion by the kidneys.' p. 61.

The second dissertation, upon the propriety of administering medicine by injection into the veins, derives a peculiar interest, from the circumstance of one of the experiments having been performed upon the person of the author. Injections of various substances into the veins and arteries of animals have been frequently practised for the purpose of determining various physiological facts, and sometimes with the view of ascertaining the probable effects of medicines introduced in this way into the system; yet little seems, so far, to have been done to settle the question as to the expediency of the practice. Some instances are related by Dr Hale, in which medicines were injected into the veins, nearly two hundred years ago, to whose efficacy effects truly marvellous were attributed. On these, however, and with good reason, he places but little reliance.

There is a great difference in the effects of foreign substances according to the part of the circulating system into which they are first introduced and the organ to whose vessels they are first distributed. When the injection is made into the carotid artery, so that the first contact is upon the brain, almost every thing, even venous blood and serum, produces instant death. Water alone, or some substance very much diluted with it, can be introduced with impunity. In other parts of the arterial system, however, where the blood is first distributed to other organs of a less delicate structure and a less important function, the consequences are not necessarily fatal. Into the veins, a great variety of substances may be injected without danger to the life of the animal employed, although, generally speaking, some sensible effects are produced by their presence in the circulating system. I have injected into the jugular veins of many dogs,' says Bichat, bile taken from the gall bladder of other dogs, which I opened at the same time. For the first few days they appeared to be weary, did not eat, were much altered, their eyes were heavy, and they were constantly lying down; but after some time, they gradually regained their former vigor. I afterwards employed human bile in these experiments; the result was the same, except that many times the animal had hiccough and vomiting some time after the injection. In one instance a dog died in

three hours after the experiment; but it was because I made use of that extremely black fluid, that is sometimes found in the gall-bladder instead of bile.'

The same experiments were repeated, with the substitution of saliva and nasal mucus suspended in water for the bile, and with similar but less marked effects. Urine, of the strongest kind, was also injected in a number of instances. It was fatal in only one, and that upon the seventh day; but the animals were usually made much sicker by it, than by the other substances employed.

'There is no doubt,' says the same writer, 'that the different substances which can be introduced with the chyle into the blood, may be the cause of various diseases. Is it not the blood which carries to the brain the narcotic principles which produce sleep? Does it not carry turpentine and cantharides to the kidneys, mercury to the salivary glands, &c.? Inject opium, wine, &c. into the veins, and you will stupify the animal, the same as if you had given them by the stomach. Physiologists were, at one time, much engaged with the introduction of medicinal infusions into the veins of living animals. They circulated, by these infusions, purgatives, emetics, and a thousand other foreign substances, the contact of which the blood bore, without occasioning any other accident to the animal, than that of vomiting or alvine evacuations, if they were emetics or purgatives, and a greater or less general derangement, if they were other foreign substances, which had no affinity with any particular organ. The caustics, as the nitric and sulphuric acids, and other very irritating substances, have alone caused death in these curious experiments.'

Of the results of all the various experiments, which have been performed by different individuals, with regard to the injection of fluids into the veins, Dr Hale observes, that they are different in different cases, and sometimes give rise to opposite inferences; but the general effect of the whole is to lead to the belief, that the effects of medicinal substances are not materially different, in consequence of the modes of their introduction into the system.'

The experiments of Fontana, for instance, offer different results from those obtained by Brodie, Magendie, and Orfila, in their investigation of the effects of the different poisons, when introduced into the circulation.

Fontana, as quoted by our author, found that the oil or waNew Series, No. 9.

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ter of the cherry laurel, although a virulent and deadly poison when taken into the stomach, is almost inert when taken into the circulation by a wound or by injection into the veins. Brodie, Magendie, and Orfila, however, found that arsenic or tartar emetic, when injected into the veins, produced nearly the same effects, as when taken into the stomach, except that they were more violent in degree. The opposite results of these different physiologists are, we conceive, attributable to the different nature of the substances employed, Fontana having used a vegetable, and the other individuals mineral poisons in their experiments. The striking differences between the different classes of poisons are sufficiently well known.

The experiments of Dr Hale were performed, with one exception, upon rabbits, and the substances injected were some of the common articles of the materia medica. Comparative trials were instituted, in which the same articles were administered by the mouth, in order to ascertain precisely their relative operation. In the first experiment two rabbits were taken, and two drachms of castor oil administered to each-to one by injection into the vein, to the other in the usual way. On the latter, no sensible effect was produced. In the former, copious operation took place from the bowels, which continued for some hours. A few days after this experiment, the same animals were made the subject of another, in which a drachm and a half of an infusion of rhubarb was injected into the veins of the one which swallowed the oil in the former experiment, and two drachms of the same infusion administered by the mouth to the other, who had previously undergone injection; in the latter, a slight operation took place within the next twenty-four hours-but in the other, no sensible effect was produced.

The sixth, seventh, eighth, and ninth experiments were occupied in ascertaining the effects of medicinal substances when taken into the stomach of rabbits. Six drachms of an infusion of colocynth, containing the strength of about twentytwo grains of that drug-four drachms of an infusion of ipecacuanha of about the same strength-four drachms of an infusion of rhubarb-two scruples of ipecacuanha in powder, were successively given to different subjects, without any operation which could decidedly be pronounced to be produced by the medicine; certainly none upon the stomach. Ten grains of tartar emetic were then administered without