years ago, while making experiments upon the urinary secretion, I found that on the sudden occurrence of a cold day after a succession of warm ones, the amount of urine secreted was very nearly doubled. One reason of this compensatory function of the skin and kidneys probably is that the secretion in both, like the secretion in other glands, depends to a great extent on the supply of blood going to them. When the supply of blood is greater, the secretion is also increased. On a warm day, or when the body is exposed to external warmth, the vessels of the skin dilate, and the cutaneous glands are freely supplied with blood. The application of cold to the surface of the body, on the contrary, causes the cutaneous vessels to contract, and thus more blood is driven to the internal organs-the kidneys amongst the

rest.

drink. At the same time the products of waste must be removed, and under such circumstances, although the skin excretes a very large quantity of water, it excretes but a small quantity of solids. The kidneys are thus put to a great disadvantage. They have still to excrete the solids: they can only do so when these solids are in a state of solution, and yet if they excrete the usual amount of water while more than usual is being thrown off from the skin, and, perhaps, less than usual is being drunk, the proper proportion of water in the body will rapidly be reduced below the normal, and its functions seriously disturbed. In order to prevent this there seems to be an arrangement in the kidney whereby water is retained after it has served its purpose of washing the solids so far through the kidneys that they can be afterwards eliminated without it. The products of tissue waste must be removed in a state of solution from the part of the kidney where they are excreted, and yet sometimes provision must be made for the water by which they are washed out being retained in the body. The urine in mammals and amphibia is liquid; in birds and reptiles it is semi-fluid or solid, yet the solid constituents are removed in solution from the urinary tubules, and the water in which they are dissolved is afterwards absorbed. In cold weather, on the other hand, the vessels of the skin are contracted, there is little or no perspiration and yet it may so happen that the individual is obliged to live on food containing a large proportion of water. This difficulty must also be met, and so in the kidney we have a provision for the removal of water without solids.

The utility of this arrangement is obvious, for although the skin has an excreting function complementary to that of the kidneys, its chief function is that of regulating the temp. of the body. When the temp. rises either in consequence of active muscular exercise or from any other cause, the vessels of the skin dilate, and if the temp. of the external air be lower than that of the body, heat is lost by radiation. The blood returns cooled from the cutaneous capillaries to the internal organs and thus the temp. is again brought down to the normal. But even when the temp. of the external air, instead of being lower, is higher than that of the body, the skin still acts as a cooling apparatus by means of the evaporation of sweat. The quantity of heat which is changed into potential energy in the process of converting liquid water into gaseous steam is very great. Five We may say then that the kidney has a threeand a half times as much heat are required to fold function: I, that of excretion of waste convert boiling water into steam as to raise products; 2, a provision for the removal of the same amount of water from the freezing to excessive water; and 3, an arrangement for the boiling point. The immense loss of heat the retention of water in the body by its reoccasioned by the evaporation of the perspira- absorption, after it has washed out the waste tion is so great that in negroes on the west products. On looking at the kidney we find coast of Africa it has been noticed that the three structures which seem to be connected skin, while perspiring profusely, is as cold as with these three functions, viz. : (1) convoluted marble, and Sir Charles Blagdon observed that tubules with epithelial cells, which in all probin a room with a temp. of 128° F. his side felt ability are the chief structures for excreting quite cold to the touch. The skin cooled by waste products; (2) the malpighian corpuscles perspiration therefore acts even with a high for excreting water along with some solids; external temp. as a refrigerating apparatus to and (3) usually one or more constrictions in the blood, and prevents the temp. of the body the tubule which may serve the purpose of from rising too high. When the external temp. preventing too rapid exit of the water, and is low the vessels of the skin contract so that thus allow time for its re-absorption in cases little blood circulates through them, and loss where its retention is desirable, as for example of heat by conduction or radiation or by pers-on a hot day and when the supply of drinkingpiration is, to a great extent, prevented. It is water is very limited. evident that on a hot, dry day, with active exertion the loss of water by the skin must be considerable, and sometimes work must be done with but a limited supply of water to

The process of secretion in the kidney was regarded by Bowman as consisting of the filtration of water from the vessels of the glomeruli into the tubule, and the excretion of

waste products by the epithelium lining the tubule. Ludwig, however, came to look upon it rather as a process of filtration and re-absorption; a dilute solution of urea and salt being, according to him, poured out from the malpighian corpuscles and gradually concentrated by the absorption of water in its passage along the tubules. This theory has so many facts in its favour that it was for a good while exclusively adopted, but latterly Heidenhain in an admirable series of experiments has shown that substances like indigo are certainly excreted by the epithelium of the tubules. At the same time Hüfner has shown by a comparison of the structure of the kidney in fishes, frogs, tortoises, birds, and mammals, that the form of the tubules closely agrees with that required for the re-absorption of water in each

of the tubule is short. This renders it probable that, while the ideas advanced by Bowman and supported by Heidenhain are in the main true, the re-absorption of water on which Ludwig lays so much stress is also an important factor in the secretion of urine under different circumstances.

But it is not only rendered probable by the facts of comparative anatomy; it appears to be proved by direct experiment. Ribbert has extirpated the medullary substance of the kidney in the rabbit while leaving the cortical substance. He has thus succeeded in collecting the urine as it is excreted by the malpighian corpuscles before it has passed through Henle's loops, and has found that the urine secreted by the cortical substance alone is much more watery than that which is secreted by the entire

I

FIG. 1.-Diagram showing the form of the urinary tubules in different classes of animals, after Hüfner. Fish. 2. Frog. 3. Tortoise. 4. Bird. 5. Mammal. The letters have the same significance in each. a. Capsule of the glomerulus. b. Convoluted tubule. c. Loop. d. Collecting tube. in 2 indicates the transverse section of the ureter.

kidney, a fact which appears conclusively to prove that water is actually re-absorbed, and the urine rendered more concentrated, during its passage through the tubules in the medullary substance.

case. Fishes have a low blood-pressure, and so the resistance in the kidney requires to be small in order to allow of the secretion of urine. Living as they do in water, they do not require any apparatus for its retention in the body. In them therefore the tubule is short In the frog and triton the arrangement of the and wide, and destitute of any constriction which would retard the outflow of fluid. In frogs there must be ample provision for the retention of water in the body, as evaporation takes place freely from their skin. In them we find, as we might expect, that the tubule, and especially the contracted part of it, is very long. In tortoises no evaporation of the skin can take place, and in them the contracted part

kidney is such as to allow of a much more complete investigation of the different factors in secretion than in mammals, becanse in amphibia the glomeruli which separate the water and the tubules which excrete the solids receive their blood supply to a great extent independently. The glomeruli are supplied by branches of the renal artery. The tubules are supplied by a vein which proceeds from the posterior ex

FIG 2.-Diagram of the circulation in the kidney of the newt. Modified from Nussbaum.

either of the artery or the vein, and observing ponding to the artery which passes directly to whether it is excreted or not, he determines

the plexus in the newt, and the latter to the branch connecting it with the afferent artery (Fig. 3). These arterial twigs are found not only near the surface of the kidney, but also in the deeper layers of the cortical substance. The third and most important channel is afforded by the arteriæ recta, which spring from the branches of the renal artery at the boundary between the cortical and medullary substance and pass into the medulla, where they form a plexus with elongated meshes surrounding Henle's loops and the collecting tubules. Near their origin the arteriæ rectæ inosculate with

same time the contraction of the arteriæ recta will probably diminish absorption from the tubules, and thus the quantity of water excreted will be increased in a two-fold manner. Circumstances modifying the Secretion of Urine. The experiments of Ludwig and his pupils have shown that the amount of urine secreted depends very closely upon the pressure of blood in the malpighian corpuscles, or, to put it more exactly, on the difference of pressure between the blood in these corpuscles and the pressure within the tubules. For if the ureter be tied so that the pressure of urine

FIG. 4.-Diagram of the tubules and vascular supply of the kidney. On the left is a tubule alone, in the middle is a tubule along with the blood vessels, on the right are blood vessels only. the venous plexus surrounding the convoluted, in the tubules is increased, the secretion is tubules.

greatly diminished, even arrested, though the pressure of blood in the renal artery be high.

A somewhat similar effect to that of ligature of the ureter is produced by ligature of the renal vein, for the blood accumulating in the venous plexus surrounding the tubules compresses them so as to prevent the flow of urine through them. A similar condition may occur from cardiac or pulmonary disease obstructing

Through these three channels it is possible for blood to reach the secreting structures of the kidney and there get rid of urea, salts, &c., without losing water by its passage through the glomeruli. On the other hand, if these vessels contract, while the size of the renal artery and the pressure of the blood within it remain unaltered, more blood will be forced into the malpighian corpuscles, and thus the quantity the venous circulation. of water excreted will be increased. At the

(To be concluded in June.)

EXTRAORDINARY, AND PROBABLY operative. In 1845, when at the age of 17, he UNIQUE, CASE OF STONE IN

THE BLADDER.

BY ALEX. PATTERSON, M.D. IN Holden's Landmarks of Surgery it is stated that the operation of dividing the tendo Achilles was first performed by the unfortunate himself, by means of a razor. The late Mr. Syme tells of a patient from the north of Scotland who, for incipient disease of the hip-joint, had had the actual cautery applied with great benefit in the Edinburgh Infirmary, and who, on the return of the pain a considerable time afterwards, having failed to induce any of the medical men in his vicinity to apply what was then considered a barbarous mode of treatment, made a poker red hot and sat down upon it. A medical man, in the agony of toothache, and at a distance from any professional friend, has been known to apply the tooth key, and wrench

fell down the well of a hoist, alighting with his legs astride an iron bar, sustaining a double fracture of the left leg, also rupture of the urethra, and laceration of the perinæum. Through the opening in the perinæum, as well as by the urethra, blood passed for a period of two weeks. Two attempts at closure of the perineal fistula were ineffectually made, and the urine continued to dribble without ceasing, compelling B. to resort to padding his clothing for the purpose of absorbing the constantly escaping urine. Several medical men saw him, but as patient was much averse to any operative procedure, nothing was attempted, although patient was aware from the year 1852 of the presence of a calculus. June 14, 1872, complaining of a pain in the bladder, sedatives were prescribed. On the 25th of the same month he was seen again, when nothing ab

normal was noticeable beyond the sinus in the perinæum. July 9 the sinus was seen to be

quested the doctor to introduce his finger through the fistula, and he would feel the stone. On passing his finger through the opening, the doctor at once felt the calculus, but his finger entered a large irregular cavity in the stone, and the patient explained by saying that he had introduced a chisel, with which he attempted to break up the mass, and had managed in this way to remove about one ounce.

out a firmly fixed molar. With regard to stone, it is told of a Dutch blacksmith, and of a German cooper, that for the relief of the in- considerably enlarged, and the patient retense and continuous pain, each performed lithotomy upon himself. There is, however, so far as I can discover, no case recorded where the patient himself tried to break down the stone in his own bladder, as was done in the case I am about to narrate. The case is also unique, in connection with the fact of a calculus of such a size having made its way out of the perinæum without any cutting opera. tion; and it is moreover unique, from its being The doctor started home for forceps, with a case where probably the largest and heaviest which to remove the stone, but during his abstone on record was removed from the human sence, whilst B. was walking about his room bladder, in which the patient recovered. in great pain, the stone suddenly burst the CASE. J. B., a retired draper, was born in perinæum, and fell heavily on the floor, breakthe year 1828, and in his youth was a factory | ing into two pieces. When expelled it weighed

VOL. IV. No. 6.