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Communicated By MARSHALL HALL, M.D., F.R.S., &c.

READ FEBRUARY 14th, 1843.

Having undertaken some experiments with the view of determining the precise cause of the appearance of albumen in the urine, I found that not only liquid albumen and blood, but coagulating lymph or fibrine also escaped into the urinary passages as the consequence of an obstruction to the return of blood through the renal vein. As the unnatural compression of the blood in the renal vessels, thus artificially produced, gave rise to phenomena identical with those constituting the primary effects of inflammation, and as the kidney seemed to present greater facilities for an experimental investigation of that important subject than any other organ of the body, I was induced to

extend my observations, and to attempt certain modifications of the experiment. The facts thus obtained will, I think, enable us to explain, with more precision than has hitherto been attempted, the true reason of the variable nature of the effusion in different instances: and as this involves physiological and pathological points of some importance, the question may not be deemed unworthy of the consideration of the Society.

As a full description of each experiment must necessarily involve much repetition, and might, therefore, tend to weary and distract the attention, I shall in this place content myself with relating those general results which bear directly on the main object of this communication: leaving the particulars of each experiment to be more minutely described in the appendix to these remarks. With the exception of the first, all these experiments were performed on the kidneys of rabbits. The animals employed varied much in age, size, and condition; and as the strength of the system exerted a very material influence in modifying the nature of the effusion, each experiment must be considered by itself, in order to arrive at a strictly accurate conclusion.

My reasons for selecting the kidney were the following:—

This organ can be readily and quickly exposed in the lower animals, and its artery, vein, and duct, (which constitute almost the sole bonds of union between it and the rest of the body,) may be separately secured by ligature: so that we not only have the circulation through the gland entirely under our command, but are, at the same time, enabled to isolate and confine the secretion, and thus prevent the possibility of error in examining the composition of the latter. Moreover, the recent discoveries of my friend, Mr. Bowman, by clearing away the mystery which had previously surrounded the Malpighian bodies, have made us well acquainted with the minute anatomy of the kidney, and have thereby enabled us more clearly to understand the mechanism of the process.

Having obtained all that I expected from obstructing the return of blood through the renal vein, I was anxious to ascertain the effect of directing, with different degrees of rapidity, an increased flow of blood to the vessels of an organ previously healthy: the passage of this blood being unimpeded by any artificial obstacle, and the organ itself being untouched. After some unsatisfactory trials, I at length obtained results precisely similar to those met with in the former series after venous obstruction.

Although the same general effects were produced in all the experiments, it will be more advantageous to consider them as arranged under two divisions.

The first, containing twenty experiments, in all of which some artificial impediment obstructed the flow of blood through the vein.

The second, comprising fourteen experiments, in which an increased determination of blood was directed to one or both kidneys, without any artificial obstacle being opposed to its free return.

After the experiments on the kidneys were performed, it occurred to me, that the observation of the effects of venous obstruction in the vessels of a frog's foot might serve to illustrate the action of the same cause in the former cases.

Accordingly, the hinder extremity of a frog was so included within two ligatures that the artery and bone were the only parts left free. There was some slight oozing of serous fluid from the wound in the ham, and the limb below the ligature speedily became red and swollen. On looking at the vessels in the web with a moderate magnifying power, the veins were seen to be much enlarged, and, as it were, prolonged into the capillaries in consequence of the accumulation of blood in, and distension of, the latter.

At first sight, the blood appeared to have lost all motion; but on examining more attentively, some small arteries were observed in the act of pouring in fresh blood; the impulse of which propelled onwards the column in the veins at each contraction of the heart. During the cessation of that action a retrograde movement occurred: the two alternate actions causing an oscillation of the contained blood.

At the end of half an hour the globules had begun to cohere, and formed by their union irregular masses and cylindrical columns, which

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