%-cr^ jw-a(t>,U RESEARCHES INTO THE STRUCTURE AND PHYSIOLOGY OF THE KIDNEY. By C. E. Isaacs, M.D., DEMONSTRATOR OF ANATOMY IN THE UNIVERSITY OF THE CITY OF NEW YORK. READ MARCH 5, 1856. "Within a few years past, great progress has been made in the pathology of the kidney, and it is therefore much to be desired that our knowledge of its anatomy should be as com- plete as possible, since every scientific examination of the diseased organ, or even of its secretion, is based upon our knowledge of the healthy structure, and must ever refer to this as its standard. We owe much to the researches of Malpighi and of Laurentius Bellini, who first discovered the tubular structure of the kidney, but we are greatly indebted to Bow- man, Toynbee, Johnson, Henle, Gerlach, Bidder, Kolliker, and other living authors, for our present knowledge of the subject. I was induced to enter upon a long-extended investigation of the minute structure of the kidney, from the fact that the high- est authorities were then, and are still at variance, with regard to some of the most important points in the anatomy of this organ. Thus the connection of the Malpighian body with the uriniferous tube, so strongly maintained by Bowman, is denied in toto by Huschke, Muller, and Hyrtl, of Yienna. The existence of ciliated epithelium in the uriniferous tubes of the higher animals, of nucleated cells upon the Malpighian coil or tuft, of a fibrous matrix, and the arrangement of the 378 Researches into the venous plexus, &c, are subjects upon which much difference of opinion exists among anatomists. It was evidently necessary that these points should be determined before we could arrive at a satisfactory physiology and pathology of the kidney. I was next led to inquire, why so many excellent observers had obtained such entirely different results, and the explanation seemed to be, that their means of investigation were insufficient. Thus some, as Bowman, had relied chiefly upon the appear- ances obtained by injection, while others had trusted almost entirely to those derived from specimens viewed as transparent objects under the microscope. Bowman, although sometimes employing the latter method, obtained nearly all his plates (except those which are diagrammatic) from specimens pro- cured by the process of injection. Toynbee, by the same method, arrived at entirely different results. It seemed, then, to me, that some other means of investigation were desirable, and especially some method by which the substance of the kidney could be rendered transpa- rent ; and that if this could be effected, it might be ascertained whose views (if any) were correct, and the true structure would probably then be determined. Accordingly, after numerous experiments with various chemical reagents, I at length arrived at the knowledge of certain processes, which have not only been useful by giving transparency to small portions and thin sec- tions of the organ, but have often enabled them to be viewed both as opaque and as transparent objects. In this manner, the observations have been rendered much less liable to error. I have not, however, limited myself to the use of these processes, but have also employed all the usual means, as injections, &c, &c. With all these aids, then, and without any preconceived theory, I entered upon an extensive and long-continued series of observations, and have given plates of the structures, as they were seen in the field of the micros- cope. I do not propose, in this paper, to enter upon all the details of the minute structure of the kidney, but at present shall merely refer to some points, to which it seems necessary at least to allude, in order that the subsequent remarks should be clearly comprehended. Structure and Physiology of the Kidney. 379 The structure of the kidney, is essentially tubular, each kid- ney, according to Huschke, containing more than two millions of minute tubes. These tubes are convoluted in the cortical portion, but straight in the pyramidal, and are each composed of a highly elastic, structureless, transparent, "basement" membrane. The integrity of the tube being of the highest importance during life, this membrane has been endowed with the quality of strongly resisting injurious influences, and even powerful chemical reagents. In virtue of this last-named pro- perty, we are enabled to show clearly the tubes of the kidney, by certain processes hereafter to be described. All the urinif- erous tubes are lined internally by nucleated epithelial cells, by means of which the urine is separated, as it is believed, from the blood of the surrounding capillaries. The epithelial cells of the convoluted are generally thicker than those of the straight tubes. Plate 1 exhibits the epithelium of the uriniferous tubes of the healthy human kidney. © © ® 0 Plate 1. 380 Researches into the The first figure in Plate 1 exhibits a convoluted tube lined by nucleated epithelial cells. The figure immediately below this shows the manner in which the cells, most of which are polygonal, are arranged. To the right of these is seen an oval- shaped cell; to the left, a cell containing two nuclei; and next to this is a polygonal cell, more highly magnified. Four sepa- rate nuclei of cells are also seen. A represents a uriniferous tube, the epithelium of which has been washed away, leaving only its basement membrane. This figure is diagrammatic. B is a transverse ring-like section of a uriniferous tube, showing its central canal, surrounded by epithelial cells. In Plate 2, A exhibits one of the straight tubes in the pyra- midal portion of the kidney. It is lined by polygonal, rounded, Plate 2. and oval nucleated cells. B shows the central canal in the inte- rior of a straight tube. C exhibits several polygonal cells. Some oval, rounded, and irregular cells, and a few separate nuclei and granules can also be perceived. Magnified 400 diameters. Most of the epithelial cells are polygonal, although many are oval, and others of a rounded or irregularly-rounded shape. They all contain finely granular matter, and a nucleus, which is itself composed of granules, among which one or two nucleoli can generally be observed. The contents of the cells are believed by Kolliker to contain albumen ; he considers the granules to be also a protein substance. The epithelium very soon becomes changed from decomposition, or by the action of water, which expands the cells, and sometimes causes them to Structure and Physiology of the Kidney. 381 burst, when the tubes are found to contain merely nuclei and granular matter. In examining the epithelium, it is therefore very important to obtain the kidney in as fresh condition as possible, and instead of water, to use a solution of albumen in water or urine. The acids dissolve the wall of the cells, leav- ing only the nuclei and granules ; the nuclei finally disappear. By the action of caustic alkalies, everything in the cell is dissolved except the granules. According to some very high authorities, the tubes of the cortical portion of the kidney are lined by the spheroidal or "glandular" epithelium. See Mr. Bowman's paper; also G. Johnson, on Diseases of the Kidney, pages 33 and 56. But in plates No. 1 and 2, it is shown that the uriniferous tubes are lined by the pavement or tesselated epithelium; and I find that, on this point, I am supported by Hassal, who says: "The epithe- lium of the tubes of the cortical part of the kidney, save within a short distance of their junction with the Malpighian dilata- tions, is composed of large and angular scales or cells, which are coarsely granular, and which form a regular layer of pavement epithelium, lining the tubes," &c.—Micros. Anat., p. 444. Kol- liker says, " The tubuli uriniferi are every where composed of the same elements, viz., a membrana propria, and a tesselated epithelium." He also remarks, " a single layer of polygonal, moderately thick cells, surrounds the cavity of the tubulus," &c. —Micros. Anat., p. 599. I believe that the description which is given in this paper will always be verified by actual observation of specimens of the kidney, provided they are in a perfectly fresh and healthy condition. It is, however, extremely difficult to meet with specimens of the kidney which are sufficiently so to exhibit the perfectly normal epithelium, and I therefore made every exer- tion to obtain the organs in a satisfactory condition, for this purpose. I am well aware that we often see the tubes contain- ing rounded, and irregularly rounded, epithelium, 2 Researches into the represents the uriniferous tube as penetrating the capsule of the Malpighian tuft, then twisting into a coil within the capsule, and finally emerging from the capsule. Gerlach says that the Malpighian capsule is not a blind termination of a uriniferous duct, but. on the contrary, a retraction, introversion, or diver- ticulum of the same membrane which forms the urine tubes. lie, however, correctly describes the Malpighian tuft as covered by nucleated cells. (See his Beitrage zur Structurlehre der Niere, in Muller Archiv., 1845.) According to Bidder, the Malpighian tuft or coil is pushed into an expanded portion of the uriniferous tube, the coil being external to the cavity of the dilated extremity of the tube, the relation of the two being similar to that of the head within a double nightcap. (See Bidder, in Muller Archiv., 1845.) This difference of opinion, even among such high authori- ties, may probably be accounted for, inasmuch as it is very diffi- cult, by employing the usual means of examination, to obtain any minute portion of the organ which will show the tube connected to the Malpighian body. Moreover, in examining any thin section of the kidney (as is usually done) for this pur- pose, it is to be remembered that the Malpighian body is always embraced in a ring of the fibrous matrix, and that at the neck of the tube, or its commencement of expansion into the capsule, is its weakest part, and where it is most easily, and indeed almost always, torn across, especially when traction is made upon it, as is usually done, in tearing out the specimen with needles. On the contrary, by using scrapings of the organ (as here recommended) agitated in water, which softens and removes many of the adhering portions of the matrix, which last holds and confines the Malpighian body, this can be washed out, and not unfrequently with the convoluted tube attached to it. (See Plates 15, 16,19, '20, 21, 22.) I may now remark, that having had no particular theory to influence my investigations, my solo object has been to ascer- tain what was the real structure, and to represent accurately what I have so frequently observed. I refer, also, with much satisfaction, to the testimony of others, to whom I showed the specimens, under the microscope, and particularly to Drs. J.P. Structure and Physiology of the Kidney. 403 Batchelder, J. M. Minor, formerly Surgeon of the U. S. Navy, Professors J. T. Metcalfe, George T. Elliot, and Alfred C. Post, Drs. Stephen Smith, J. S. Goulay, John T. McNulty, George A. Peters, T. C. Finnell, and many others, who were satisfied that the structure was strictly that which has been represented in the plates here given. Within the last week, I have met with a paper on the structure of the kidney, in some of the mollusca, and in birds and serpents, by Dr. Busch, of Berlin, in the last August number of Midler's Archiv, for 1855. He says:—" My experiments on snakes have fully convinced me that the glomerulus (or Malpighian coil) is truly situated in the expanded end of a uriniferous tube." " Dass der glomerulus wirklich, in einer kapsel, dem erweiterten ende, eines Harn canalchens, gelegen sei." His description is very similar to that of Bowman, but he differs from him in representing the Malpighian tuft as covered by nucleated cells. A plate of the structure in the snake is also given. On the termination of the convoluted uriniferous tubes. The convoluted tubes form loops, and also become continuous with the straight tubes, but I have never seen blind extremities, or the anastomoses of the tubes, as described and figured by Toynbee and others, except in the kidney of frogs, fish, and turtles. I would not wish, however, to be understood as deny- ing their existence. On the question whether nucleated cells exist upon the Malpig- hian tuft or coil of capillaries. Much difference of opinion on this point still prevails among anatomists, and, as will be seen hereafter, the determi- nation of this subject is very important in reference to the physiology of the kidney. The epithelium of the tuft is, perhaps, best seen in the kidney of frogs, snakes, etc., but I am not aware that any anatomist has satisfactorily demon- strated it in that of the higher animals. 404 Researches into the In the investigation of this subject, it seemed to be very difficult to ascertain the true>rrangement, and for the following reasons:—In looking at the Malpighian body, which consists of the tuft or coil of capillaries, and the expanded extremity of the uriniferous tube, or the capsule, as it is called, we observe a number of cells, which seem to lie on the surface of the Malpighian body, but which are really on the inner surface of the capsule. See Plate 19. As the capsule embraces the tuft or coil, and ordinarily is closely applied to it, it results that the cells lining the interior of the capsule must conceal those which are on the tuft, if indeed such there exist. It would thus seem almost impossible, in looking at a Mal- pighian body, to decide whether the cells which we see appa- rently upon its surface, are really those on the inside of and lining the capsule, or whether they are on the tuft, and are perceived through the transparent capsule, or, lastly, are they the cells, both of the tuft and of the interior of the capsule ? After much reflection as to the best plan of determining this point, I adopted the following processes:— 1. By injecting watery and etherial solutions into the ureter, I succeeded in bursting the capsule, the Malpighian tuft or coil having been previously only slightly, and as was intended imperfectly injected from the artery. Epithelial cells could, then be seen upon the uninjected and transparent edges of the tuft or coil. Plate 24, Fig. 1, exhibits a Malpighian tuft. Broken frag- ments of the injected vessels are seen within it. They had been injected with chrome yellow, and appear black when the specimen is viewed by transmitted light. The uriniferous tube had been distended by the injection from the ureter, and its expanded extremity, or capsule, had been burst, and can be perceived lying in shreds at the sides of the tuft, which is now uncovered by the capsule. Nucleated cells can be seen upon the naked and uninjected parts of the tuft. From the kidney of the black bear. Magnified 80 diame- ters. Fig. 2. In this specimen the capsule had been scratched off with a needle, and then the naked tuft somewhat torn under Structure and Physiology of the Kidney. 405 the microscope. In Fig. 3, some small fragments of the tuft are here seen with nucleated cells on their surface. JFy?./ Plate 24. 4. The capsule was torn off from a Malpighian body with a needle. In doing this, the capsule became reversed, so as to give a view of its internal surface, upon which small nucleated cells could be clearly and distinctly seen. The surface of the naked tuft was covered by cells of much larger size than those upon the interior of the capsule. Upon the application of dilute nitric acid, the wall of the cells of the capsule was dis- solved, while comparatively little effect was produced upon those of the tuft, thus showing a difference in tlieir chemical 406 Researches into the constitution and organization. In Plate 25, A is the uriniferous tube; B, cells on the tuft; C, reversed and inner surface of the Plate 25. capsule, covered by cells differing in their appearance and chemical reactions from those on the tuft. From the kidney of the raccoon. Magnified 400 diameters. 5. Fine scrapings of the kidney were agitated occasionally for two or three days, in a test tube, the water having been frequently changed. By this method, the epithelial cells within the capsule were washed out, so that the space thus left between the tuft and the capsule became filled with water, which had Boaked through the capsule. See Plate 26. At A is seen the uriniferous tube. A few cells yet remain in its interior. B denotes the capsule. At C is perceived the minute arterial vessel which enters the tuft. By slight agitation, while the specimen was floating in the water, under the microscope, it could be rolled over and over, Structure and Physiology of the Kidney. 407 so as to show various points of the surface of the tuft, covered Plate 26. by nucleated cells. As it repeatedly turned over in the water, it resembled a ball, suspended in a transparent bag, or bladder of water, and slightly swaying from side to side. From the kidney of the cat. Magnified 250 diameters. By the different processes just mentioned, I consider the existence of nucleated cells upon the surface of the Malpighian tuft, and, consequently, its analogy with the other secreting organs, as conclusively demonstrated. Conclusions as to the Functions of the Malpighian Body. According to Mr. Bowman, the Malpighian coil or tuft of capillaries lies entirely naked in its capsule, and its office is simply that of separating water from the blood, while the urea, lithic acid, and salts, are separated by the epithelial cells of the tubes from the blood of the venous plexus which surrounds them. These views, and some others, of Mr. Bowman, which will soon be presented, have been so extensively adopted, and 27 408 Researches into the copied into the text-books on physiology, that they deserve our most attentive consideration. 1. It is probable, that in other organs, water is never sepa- rated from the blood, simply as such, in any case whatever; but that it then always contains albuminous substances, and certain salts, and not unfrequently other materials. Nor do we find that a peculiar or special arrangement of vessels is required, even for the exhalation of serous fluids, but that, on the contrary, they may exude, or pass by simple exosmosis, through the minnte vessels of any of the organs which are composed of soft and yielding tissues. Thus, the cerebro-spinal fluid per- meates the vessels of the pia mater and the areolar ti&sue, and the serous membranes are moistened by a fluid, or, even in health, may contain a small quantity, exhaled from capillaries which are most simple in their arrangement. On the contrary, . the Malpighian coil or tuft is so complex, and so peculiarly formed, that in man, and in the higher animals, we shall find that no organ except the kidney contains the same, or even a similar structure. It would, therefore, scarcely appear neces- sary that the Malpighian tuft, which is so complex in its organi- zation, should be needed merely for the purpose of separating water from the blood, which could be effected by a much more simple arrangement of vessels, as well as by the entire and extensive epithelial surface of the uriniferous tubes. 2. The presence of peculiar nucleated cells upon the Mal- pighian coil or tuft, would seem to denote that some of the constituents of the urine, besides water, are secreted by them. 3. In birds and reptiles the urine is secreted either in the semi-fluid, or, as in the latter class, almost in the solid form. Simon says: "The urine of serpents is excreted as a white, pultaceous, earthy mass, which soon stiffens on exposure to the air. It is composed, for the most part, of uric acid in combina- tion with potassa, soda, and ammonia, together with phosphate of lime." (Simon, p. 502.) According to Prout, the urine of the boa-constrictor contains more than ninety per cent, of uric acid. The urine of the rattlesnake, analyzed by Simon, was composed almost entirely of uric acid and the urates. (See Simon, p. 54.) According to Jos. Jones, who has analyzed the Structure and Physiology of the Kidney. 409 urine of several species of snakes, their urine contained uric acid, always in combination with ammonia; he could not detect the presence of urea. (See his very valuable paper in the American Journal of Medical Sciences, April 1855.) Yet in these animals the Malpighian bodies exist, not only in the cor- tical portion, but throughout the entire kidney; and if, as asserted, their function is merely that of separating water from the blood, this fluid should be in excess; but it appears, on the contrary, that the urine is excreted almost in the solid state. 4. Will the entrance of foreign substances into the circula- tion, and their detection in the kidney and in the urine, throw any light upon the function of the Malpighian coil or tuft of capillaries? Let us examine carefully the following facts. According to Simon, after administration of the following substances, they can be detected in the urine:—Iodine and bromine, in combination either with ammonium, sodium, or potassium. Sulphur, ferrocyanide of potassium, salts of arsenic, antimony, iron, mercury, nickel, gold, silver, tin, lead, bismuth, copper, and manganese, have all been found in the urine. This was also the case with the organic acids—as the tartaric and citric acids. Meconic acid has been detected in the urine of animals poisoned with opium, as have also morphine and qui- nine. Coloring and odorous, or volatile substances, have often been recognized in the urine, as indigo, gamboge, rhubarb, madder, Indian fig (which colors the urine blood-red), garlic, turpentine, cubebs, and balsam copaiba. Alcohol has very often been found in the urine. Lehman, after taking phloridzin, discovered hippuric acid and oxalate of lime in his urine. 1 have myself repeatedly swallowed solutions of the ferrocyanide of potassium, and in fifteen or twenty minutes ascertained its presence in the urine by its striking a blue color with the salts of iron. I have also frequently taken small quantities of ben- zoic acid, and found, on microscopic examination of the urine, that it had been changed and separated from the kidney under the form of crystals of hippuric acid. Urea has been given internally by some of the French phy- siologists, and has acted as a powerful diuretic, and on such occasions has been found in large quantity in the urine. Now 410 Researches into the then, it is admitted by Mr. Bowman that diuretics must enter the circulation and pass along with the blood of the renal artery into the Malpighian body. He even says: " Diuretics appear to act specially upon the Malpighian body, and various foreign substances, particularly salts, which when introduced into the blood, pass off by the urine with great freedom, and exude, in all probability, through this bare system of capillaries. The structure of the Malpighian body indicates this ; the escape also of certain morbid products, occasionally found in the urine, seems to be from the Malpighian tufts. I allude especially to sugar, albumen, and the red particles of the blood; the two first of which would transude, while the last would escape only by rupture of vessels." (See Bowman, Philosophical Transac- tions, 1842.) It is then conceded, and we have every reason to believe, that these foreign substances do actually pass through the renal artery, and consequently through the Malpighian tuft or coil; and if this tuft can separate all the various substances above enumerated as having been found in the urine, and especially the various salts and the urea, are we not justified in believing that in the performance of its normal function it does some- thing more than merely separate the water from the blood \ The following is an interesting illustration of the capability of the Malpighian tuft for the separation or elimination of cohering matters. Within a few days past, my friend, Dr. J. C. Hutchison, of Brooklyn, has presented me with some, speci- mens of diseased liver and kidneys taken from the body of a man who had been very intemperate for the last twenty years. The patient was deeply jaundiced for some time previous to death; the kidneys were slightly indurated. On making a microscopic examination of very thin sections of the kidney, I found that some of the convoluted uriniferous tubes contained particles of bile, and that some of the epithelial cells were stained of a deep yellow color by this substance. The Malpig- hian bodies were of a slight yellow or brassy color. On apply- ing Pettenkoffer's test, the Malpighian bodies and the colored contents of the tubes showed a play of colors, and finally were reddened by the action of nitric acid. Thin sections of the Structure and Physiology of the Kidney. 411 kidney, steeped in water, colored it slightly yellow; and this fluid, acted on by nitric and by muriatic acid, assumed the usual varying colors, thus fully demonstrating the presence of bile. These facts seem to prove that the Malpighian tuft has the power of separating the coloring matter of the bile, and it would be difficult to explain its presence in the urine except on the supposition that it had passed through the coil or tuft. Lastly—Simon, Marchand, and many others have detected urea in the blood of healthy animals. Yalentin says: " It may be recognized in the blood, in the saliva, in the aqueous and vitreous humors, in dropsical fluids," &c. In cases of Bright's disease, and especially after extirpation of the kidneys, it is found in the blood in large proportion. According to Dr. Gar- rod, uric acid also exists ready formed in the blood, even in health, and can always be easily detected in that of gouty patients. The coloring matters Of the urine, and the various salts, as the phosphates, sulphates, and chlorides, pre-exist in the blood. This is also the case with the kreatine and kreatinine, which are derived from the disintegration of the muscular tissues. It is, then, proved that all the elements of urine are first formed in the blood, and subsequently separated by'the kidney. Thus the blood wrhich contains them must pass through the renal artery and the arterial terminal twig which supports the Mal- pighian body. The blood passes slowly through this vascular coil or tuft, and its velocity is also retarded in consequence of the small size of the " vas efferens," or the vein which returns the blood of the tuft into the venous plexus. (See Plate 10.) Here also the cells which lie immediately upon the tuft aid in the separation of the elements of the urine. (See Plate 25.) If any constituent of the urine should escape separation from the blood while in the Malpighian body, it must then pass through the vas efferens into the venous plexus, the arrange- ment and function of which will now be considered. It has been already stated, that according to Mr. Bowman, whose views are entitled to the highest respect, and have been almost generally adopted, the urea, lithic acid, and salts 412 Researches into the are separated by the epithelial lining of the tubes from the blood of the venous plexus which surrounds them. The minute vein which returns the blood of the Malpighian tuft or coil, or the " vas efferens," as it has been termed, is similar in its nature to the vena porta, and the blood of the venous plexus to that of portal blood; or, as he observes, " each efferent vessel is a portal vein in miniature. In support of his theory, he states that, " in serpents the kidney receives not only a renal artery, but also a ' large renal portal vein,'' bringing, for the secretion of urine, the venous blood of the hinder parts of the body, and giving off the capillaries which ramify upon the urine tubes." —(Bowman, Philosophical Transactions, 1842. See Plate 27, which is a view of the minute structure of the kidney in the boa-constrictor.) In Plate 27 A is a small branch of the r^nal artery; Af a Plate 27. small twig from it, passing on to expand into and form the Malpighian tuft or coil of capillaries; Ef\& a vein returning the blood of the Malpighian coil; Mthe coil itself; PFthe portal vein; iTFthe emulgent or renal vein ; Cthe capsule of Structure and Physiology of the Kidney. 413 the Malpighian coil; U the ureter; T the uriniferous tube lying in the midst of the minute veins which pass from the portal to the emulgent or renal vein. In further explanation of his views, Mr. Bowman remarks: " Thus the efferent vessels of the Malpighian bodies are radicles of the portal vein, and through the portal vein empty them- selves into the plexus surrounding the uriniferous tubes. The only real difference between this form of kidney and that of the mammalia is that here is a vessel bringing blood that has already passed through the capillaries of distant parts, to be added to that coming from the Malpighian bodies, and to cir- culate with it through the plexus surrounding the tubes. The efferent vessels of the Malpighian bodies run up the surface in order to throw their blood through the whole extent of the capillary plexus, &c. The emulgent vein of the kidney an- swers to the hepatic vein of the liver. But in the kidney of the higher animals the portal system has only an internal source, and the artery supplying it is proportionally large." These views of Mr. Bowman, so generally admitted at the present day, will now be considered, and it is with much diffi- dence, that I feel obliged to differ in opinion with that very distinguished physiologist. And firstly, as»to the vein and v plexus, which it is said that the ^ vena porta sends to the kid- ney, and which ramifies upon the uriniferous tubes," &c. The current of blood in the portal vein, coming from the lower parts of the animal and passing upwards, must be towards the liver. The direction of the current in the renal vein must be from the kidney towards the vena cava ascendens. A plexus is found to intervene between the vena porta and the emulgent vein. (See Plate 27.) From the blood of this plexus, it is believed that the urine is separated by the action of the epithe- lial cells which line the uriniferous tubes. Now, it may be asked, why should this plexus exist, if not for this purpose? To which it might be answered, that by means of this vascular arrangement, a certain amount of portal blood, which is not required for the function of the liver of the serpent, or which might be injurious to its action, can be diverted from that organ by passing through the plexus into 414 Researches into the the emulgent vein. This is also probably a channel by which the lower organs of the body may temporarily relieve them- selves when congested, by allowing the blood which returns from them into the portal vein to pass into the renal vein, and so on into the current of the general venous circulation. The " vas efferens," or the minute vein which returns the blood of the Malpighian tuft of the serpent, passes into or joins the portal vein. (See Plate 27.) Now, even in the boa, the blood of the " vas efferens" cannot strictly be regarded as portal blood, or at least, it does not as such influence the secretion of urine, unless perhaps when some obstruction occurs in the portal vein. Blood would then pass backwards, or regurgitate from the portal vein into the " vas efferens." But this would be accidental, and would not occur under ordinary'circum- stances. On the contrary, the blood of the " vas efferens" should be regarded as renal blood. It is, in fact, merely the returning blood of the Malpighian tuft, passing towards and emptying into the portal vein. (See Plate 26.) But the ques- tion might be asked, Why then does a portion of the venous blood of the kidney of the serpent return through the vas efferens into the portal vein ? To this it may be answered, that inasmuch as scarcely any- thing, with the exception of uric acid and urate of ammonia, is separated from the blood of the serpent in the process of urinary secretion, the venous blood of the kidney remains loaded with the elements of urea and of other products resulting from the decomposition of the tissues, and especially from the food of which these animals consume enormous quantities at a time. These elements, then, added to the blood of the vena porta, contribute to it something which is useful in the formation or secretion of the bile. The kidney of the serpent, therefore, by sending or contributing a portion of its venous blood to the liver, stands nearly in the same relation to that organ as do the chylopoietic viscera. Having thus far dissented from the views of Mr. Bowman respecting the peculiar vascular arrangement in the kidney of the serpent, it next remains to be considered whether a similar structure exists, as has been stated, in the human kidney. In the latter we find no communication Structure and Physiology of the Kidney. 415 between the portal and renal veins, nor any venous plexus resembling that which exists in the kidney of the serpent. Next, as to the analogy which has been drawn between the vas efferens of the kidney of the serpent and the same vessel in the human kidney, or in those of the higher animals. The vas efferens in the serpent returns its blood into the portal vein. The vas efferens of the human kidney returns its blood into a plexus, which may be said to be composed of the minute radi- cles of the branches of the renal vein. Thus far there is no resemblance between the vascular arrangement of the kidney of the boa and that of the higher animals. But this has been thought to exist between the vas efferens of the human kidney and the vena porta, and it has even been said, that "each efferent vessel is a portal vein in miniature." In order to prove this assertion, it would be necessary to show that the vas efferens originates by very many branches from the Malpig- hian tuft, in a manner similar to that by which the vena porta commences: viz., by numerous radicles from the abdominal viscera. Mr. Toynbee says : " In the healthy corpus Malpig- hianum it is impossible to ascertain with precision the manner in which the emerging vessel of the corpus (coil) takes its rise from the rete or coil; but, from an examination of the Malpig- hian body when morbidly enlarged, it would appear that it springs from the convoluted vessels by radicles of smaller dimensions than the convolutions themselves. In some in- stances the rete or coil seems to be formed by a single branch of a single vessel in which the artery terminates." On examination of many injected Malpighian tufts, I have generally seen the vas efferens emerging from the tuft at a point very near to that at which the minute arterial twig, which supports the tuft, enters into it. (See Plates 3 and 9.) I have never been able clearly to perceive the mode in which it origi- nates, and it is very difficult to ascertain this point. I have, however, never seen it commencing by radicles similar to those of the vena porta. But even allowing the arrangement to be exactly as described by Mr. Bowman, the analogy would appear to be a forced one, for the vena porta conveys blood from the intestines to an organ of entirely different structure, 416 Researches into the viz., the liver; whereas the vas efferens conducts blood from the Malpighian body of the kidney to a plexus belonging to the same organ, and in microscopical proximity to it. Moreover, as it emerges, it is frequently joined by an arterial branch ; so that, after all, the so-called venous plexus is not strictly such, but contains a mixture of arterial and venous blood. (See Plate 3.) It may then be concluded that the interpretation of the peculiar structure in the kidney of the boa-constrictor is not satisfactory, and'that no such structure exists in the human kidney, or in that of the larger animals, and that the supposed analogy of the vas efferens of the human kidney with the vena porta should not be admitted, inasmuch as its mode of origin is not clearly ascertained, and at least does not appear to be similar to that of the vena porta ; and even if it were as stated, it would not then be proved that its function was similar to that of that vessel. The reasons for this view have already been given. It has been attempted to explain the physiology of the human kidney by considerations of structure in the kid- ney of the boa-constrictor, an animal presenting an immense difference in its organization from that of man, or of the higher animals. The facts and arguments which have here been pre- sented, in opposition to this view of the subject, it is hoped will be found to be satisfactory. It will be remembered, that to the epithelial cells which line the uriniferous tubes has been attributed the power of separating the urea, lithic acid, Ac, from the blood of the venous plexus. How probable this opinion may be will appear from a consideration of the following facts: 1. The Malpighian tuft is covered by nucleated cells. 2. The proximate elements of the urine exist ready formed in the blood. 3. The blood thus containing these elements, as urea, lithic acid, salts, Ac, &c, must pass into the renal artery, and consequently into the Malpighian tuft, where, owing to the arrangement of this coil of vessels, and also to the small size of the vas efferens, its course must be retarded. The constituents of the urine are thus placed under the most favorable circumstances for escap- ing from the tuft. 4. Foreign substances introduced into the Structure and Physiology of the Kidney. 417 blood must necessarily pass into the tuft, and some (as the coloring matter of the bile) have actually been detected in it. From the foregoing facts it may be inferred that the Mal- pighian tuft separates many of the proximate elements of the urine (in combination with water) from the blood. It appears to be very difficult, or even impossible, to arrive at any other conclusion. There then remain other elements of the urine, which may perhaps be separated from the blood by the action of the cells of the tubes, as generally supposed. The argument, however, in support of this view, that these cells belong to the spheroidal or "glandular" variety of epithelium, and must therefore necessarily secrete the proximate elements is unten- able, as it has been proved that the epithelium lining the tubes is really of the tessellated kind. On the other hand, this fact is not an objection to the opinion in favor of their secreting agency, because, as has been already mentioned, the bile, which is the most complex of all secretions, is separated by the hepatic cells, which are qf very irregular form, and resemble tessellated epi- thelium. It is not probable that all the elements of the urine should pass through the renal artery and the Malpighian tuft, which appears to be specially constructed for their separation, and to offer every facility to their passage into the capsule of the uriniferous tube, merely that they might reach the venous plexus, where they could then be separated. However, it is not impossible that some one or more constituents of the urine, combined with water, may be separated by the agency of the epithelial cells of the tubes, as generally supposed, and perhaps also any element which may have escaped separation while passing through the Malpighian tuft. Comparative anatomy and chemical pathology will hereafter throw much light upon these obscure points of physiology. 418 Researches into the Of the Fibrous Matrix of the Kidney. Some of the most accurate observers have failed to detect the areolar, or the fibrous tissue, in the proper substance of the kidney. Henle, a most learned and excellent histologist, has even said: " Je n'ai jamais apercu la moindre trace de tissu cellulaire entre les canalicules uriniferes."—Henle, Anat. Generate, tome ii. p. 512. The fibrous matrix of the kidney was first described by Mr. Goodsir in 1842. and although this structure is of the greatest physiological and pathological im- portance, as will be shown hereafter, yet its existence has been, and is even now, doubted or denied by several authors. Pro- fessor Lionel Beale, of King's College, London, after describing the matrix, in his excellent work on the microscope, published in 1854, observes: " Of late much discussion has arisen with reference to the presence or absence of a fibrous matrix in the healthy human kidney, and observers are not agreed as to which is really the case." Dr. George Johnson, in his valuable work on the kidney, remarks, that Rokitansky has fallen into the very grave error of representing the normal fibrous matrix as a product of dis- ease. (Page 321.) And again, he states that Frerichs (a very high authority) doubts even the existence of the normal fibrous matrix. It appeared to me, therefore, that this subject required fresh investigation. I have never satisfactorily succeeded in exhibiting it by following the directions usually given for this purpose. It can, however, be always easily and distinctly shown by the following process : Very thin slices of the kid- ney are to be made with Yalentin's knife, put into a long test- tube about one third full of water, and agitated from time to time for two or three hours. Prepared in this manner, a thin section exhibits under the microscope a kind of mesh, network, or honeycomb arrange- ment—the cells of the honeycomb, however, having no bottom. In the natural condition of the kidney, the smaller cells or openings transmitted the tubes; the larger cells or opening^ were occupied by the Malpighian bodies; which last, together Structure and Physiology of the Kidney. 419 with the tubes, have now been washed out of the cells, although a few are often seen still remaining in situ. (See Plate 28.) Plate 28. This plate exhibits the fibrous matrix of the kidney of the rat. The smaller rounded spaces are for the tubes, the larger openings for the Malpighian bodies. Three of the last are also seen. Nucleated epithelial cells are seen through the capsule, and apparently upon the capsule, but really within it. Magni- fied 250 diameters. Plate 29 shows the fibrous matrix of the kidney of the dog. Plate 29. 420 Researches into the A Malpighian body is seen in the centre, and surrounded by its own investment of fibrous tissue, and also by numerous ring-like cells for the tubes. Magnified 80 diameters. I'laii Ay). Plate 30 shows the fibrous matrix of the kidney of the grey rabbit. Magnified 80 diameters. Plate 31. Plate 31 exhibits the fibrous matrix of the kidney of the Structure and Physiology of the Kidney. 421 raccoon. The cut orifices of capillaries can be seen in the meshes of the matrix. Magnified 400 diameters. Plate 32 shows the fibrous meshes of the kidney of the grey squirrel. The Malphigian bodies and the uriniferous tubes of this animal are very small. The epithelial cells which are on Plate 33. the inner surface of the capsule and on the Malpighian tuft, are seen with great distinctness through the transparent cap- sule. Magnified 400 diameters. Plate 33 shows the fibous matrix of the kidney of the hog. At A is a view of a very thin section of the kidney. Small rounded openings, for the passage of the tubes, and two larger ones for the Malpighian bodies, are here observed. At B an artery divides into terminal branches, each of which supports a Malpighian body, enclosed in a ring of the matrix. This is magnified about forty diameters. Plate 34 shows a Malpighian body lying in its matrix. Nucleated cells can be perceived apparently upon its surface. Magnified 250 diameters. This was also taken from the kidney of the hog. 422 Researches into the Piatt 34. Plate 35. Structure and Physiology of the Kidney. 423 Plate 35 represents the fibrous matrix of the kidney of the sheep. A Malpighian body can be seen lying in its capsule, which, after surrounding it, passes down to become continuous with the basement membrane of the tube. The epithelial cells lining the tube have been washed away. Magnified 250 diameters. Plate 36 exhibits a view of the fibrous matrix of the kidney of the ox. The large rounded opening, marked A, contained Plate 36. a Malpighian body. The tubes passed through the smaller rings. At B is perceived a Malpighian body. The uriniferous tube is seen to expand and form the capsule, which is enclosed dn a ring of the fibrous matrix. Magnified 400 diameters. [28 . 424 Researches into the Plate 37 shows the fibrous matrix of the kidney of the horse. Magnified 400 diameters. ' Plate 37. Plate 38 shows the fibrous matrix of the kidney of the elk. Magnified 400 diameters. Plate 38. Plate 39 exhibits the fibrous matrix of the kidney of tho moose. Magnified 350 diameters. Plate 40 shows the fibrous matrix of the kidney of the black bear. Magnified 400 diameters. Plate 41 exhibits the fibrous matrix of the healthy human kidney. This section was made somewhat obliquely, so that it shows the matrix of the straight tubes which were contained in the elongated spaces, marked F. The rounded spaces for the convoluted tubes, and a larger one for the Malpighian body are also seen. Magnified 250 diameters. From a boy, sixteen • Structure and Physiology of the Kidney. 425 Plate 39. years of age, killed by falling from a house. This kidney was examined a few hours after death. Plate 40. According to my experience, it is rare to find a human kidney which is perfectly healthy. This is particularly the case 426 Researches into the Piatt 11. in subjects in the dissecting-room, and in those who have died in large hospitals. Out of more than 500 subjects which I have examined in this city, I have seen but very few in which tlfe kidney could be regarded as in an entirely healthy condi- tion. Being very anxious to procure a perfectly healthy speci- men of the organ, from which I could exhibit the matrix, I obtained a considerable number of kidneys from the bodies of persons killed by violence and accidents, but these were also found to be diseased, most probably from intemperance, &c. I at length procured the healthy organs, from which the present view of the matrix is here given. From what has now been said and exhibited, it is evident that the fibrous matrix is really the skeleton, or frame-work, of the kidney. It consists of myriads of septa, or partitions, cross- ing each other in various directions, so as to form elongated spaces for the straight tubes, or rounded spaces, cells, or rings for the Malpighian bodies and convoluted tubes. Structure and Physiology of the Kidney. 427 In certain pathological conditions of the kidney, it becomes diminished in size and indurated; its surface is irregular and covered with small projecting points, like variously-sized shot. This condition is not unfrequently seen in old drunkards, and would seem to be analogous to cirrhosis of the liver, and pro- bably induced in a similar manner; the alcoholic fluid passing through the tubes of the kidney, and by continued irritation producing crisping, or irregular contraction of the meshes of the matrix, which consequently constrict the tubes and the Malpighian bodies. Plate 42 shows the fibrous matrix of the kidney of a negro. 428 Researches into the It was in a condition precisely similar to that just described. The Malpighian bodies were of various size—some of them very small. (See letters A A A.) The thickness of the meshes of the matrix was much greater than in the preceding specimen. Magnified 250 diameters. m m Thickening and induration of the matrix may produce inju- rious effects otherwise than by constriction of the tubes and Mal- pighian bodies. The minute vessels and capillaries pass through the substance of the fibrous rings. Consequently, induration and contraction of the matrix, by direct pressure on the vessels, must greatly interfere with the circulation, nutrition, and secre- tion of the kidney, and thus various morbid products, as blood, albumen, pus, tubular casts, &c, may be found in the urine. Plate 43 exhibits the fibrous matrix of the kidney of the sheep (cross section). The kidney had first been injected with Plate 43. vermilion through the renal vein, and then thin sections of the organ were carefully washed. The dark, round points, seen in the substance of the rings of the matrix, are the cut orifices of the injected capillaries of the venous plexus. They appear dark when a thin section is viewed under the microscope by transmitted light. Two of the fibrous rings, A B, contain a ring-like section of a uriniferous tube, which is still lined by its Structure and Physiology of the Kidney. 429 epithelium, and its canal may be seen in the centre. Magnified 400 diameters. To examine into the nature of the fibrous matrix, it is necessary to obtain a portion of it unconnected with the tubes, Malpighian bodies, or other parts. After repeated washings and examinations under the microscope, I at length found some thin sections free from any other tissue. On the addition of dilute acetic acid, the matrix became swollen, cloudy, softened, and easily torn or broken, and a number of elongated bodies, or nuclei, appeared scattered through it. Plate 44 shows the fibrous matrix of the healthy human kidney, treated with acetic acid. Magnified 250 diameters. Plate 44. Small portions of the matrix, teased out with needles, in a drop of water, and then examined with the microscope, presented the appearance usually exhibited by white fibrous tissue in other organs, with this exception, that no trace could be found in the matrix of yellow elastic tissue. This last would probably have been injurious, by compressing the Malpighian bodies, and more especially the vessels and uriniferous tubes. It may be presumed, also, that the elasticity of the latter would render the presence of the yellow tissue unnecessary. Hassal, how- ever, says that, " the tubes as well as their globular termina- 430 Researches into the tions, are all enclosed in a frame-work constituted of a nucleated form of elastic tissue."—Micros. Anat., vol. i., p. 443. This is very different from what I have observed. While. engaged in examining the matrix, I carefully compared it with the white fibrous tissue of tendon, and also with the areolar tissue surrounding the renal artery of the ox just before it enters the hilum, or fissure of the kidney. It is very similar in appearance to both these tissues, and indeed so much resem- bled the areolar tissue, that no one could have distinguished the difference, with this exception—that in the last could be perceived some fibres of the yellow elastic tissue, while none of these could be seen upon the most careful examination of the matrix. These tissues all exhibited similar reactions with acidsi and alkalies, and nuclei of the same form and character. Plate 45 shows the areolar tissue around the renal artery of the ox, acted on by dilute nitric acid. The elongated nuclei Plate 45. are seen in the white and waving fibrous tissue. The yellow, elastic fibres are curled like the tendrils of a grape-vine. When the matrix was treated with nitric acid, similar nuclei appeared, but the matrix was not so much softened, or so easily torn or broken. Magnified 250 diameters. Structure and Physiology of the Kidney. 431 Plate 46 represents the matrix of the healthy human kid- ney acted on by dilute nitric acid. Magnified 250 diameters. Plate 46. The action of muriatic and phosphoric acids was similar to that of the nitric. When portions of the matrix were boiled in water, with one or two drops of sulphuric acid, they shrunk slightly, became soft, easily broken; the rings of the matrix could still be seen, the nuclei very faintly. The prolonged action of all these acids was to render the matrix cloudy and granular, while the nuclei disappeared. They were, however, invariably restored by the addition of the carbonate of potassa. From what has preceded, we may conclude that the matrix of the kidney is composed entirely of white fibrous tissue, with- out any admixture of the yellow elastic tissue. 1 have repeat- edly examined it, in many animals and in man, and find it to be in all apparently the same structure, varying only in the size of its meshes or rings, according to the dimensions of the tubes and Malpighian bodies, which differ in. all these animals. From the foregoing remarks, it is evident that a correct know- ledge of the fibrous matrix is of great importance, and that its microscopical and chemical investigation, in all cases of diseased kidney, would probably furnish interesting and valuable results. Something may here be said relative to the proper sub- stance, or parenchyma of the kidney. This consists: 1. Of the uriniferous tubes; 2. Of the arteries, veins, and intermediate capillary plexus—all which have already been described; 3. Of 432 Researches into the the lymphatics—of which we know almost nothing, although Hyrtl thinks that they communicate with the Malpighian bodies; 4. Of the nerves—whose mode of termination is un- known, at least in the higher animals. Mr. Toynbee believes that the nervous filaments end by becoming continuous with the parenchyma of the organ, " precisely in the same way as he has observed those in the tail of the tadpole to become directly continuous with the radiating fibres of stellate corpus- cles, and the filaments from the corpuscles to communicate with each other." 5. Of the plasma of the blood; 6. Occa- sionally a few small rounded and granular nuclei can be seen scattered in the substance of the matrix. Lastly, it may be asked, whether any other structure enters into the composition of the parenchyma ? Some have supposed that certain peculiar corpuscles, or cells, were also present in this substance; but, after very many and repeated observations, I have not been able to perceive any other cells than those contained in the uri- niferous tubes. These cells seem to be united by means of a slightly opaque, amorphous fluid, containing granules, and which is rendered transparent by dilute boiling acids. Many careful observations have not enabled me to discover any other structures entering into the composition of the parenchyma or proper substance of the kidney, than those above stated. Before concluding this treatise, it may be well to consider what facts or deductions have been brought forward which may be regarded as new, or of an original character, or as tending to confirm or disprove the views of the best authorities on the subject. 1. Certain processes have been recommended for displaying the structure of the kidney, which, so far as I know, have not hitherto been employed. At the same time, views exactly similar (although not always so clear and extensive) have been obtained in the most simple manner, and where no chemical agent has been used, so that the various processes, although entirely different, yet confirm each other. 2. Contrary to the opinions of some of the highest authorities (see G. Johnson, On Diseases of the Kidney, p. 35), the epithe- lium lining the tubes of the kidney has been shown to be of the Structure and Physiology of the Kidney. 433 pavement or tessellated variety. (See Plates 1 and 2.) The physiological inferences from this anatomical fact have already been considered. 3. Ciliary motion, although weak and imperfect, has been seen in the kidney of the higher animals. 4. I cannot but consider that the views of Mr. Bowman concerning the connection of the Malpighian body with the uriniferous tube are indubitably correct, inasmuch as I have observed this arrangement so very often, and under circum- stances entirely different from those under which his observa- tions were made. His plate, however, showing the connection of the expanded extremity of the uriniferous tube (or the capsule) with the Malpighian tuft, together with the "vas efferens" returning the blood of that tuft into the venous plexus, and which has been so generally copied into the text- books on physiology, is merely a diagram, or " plan," and is so called in his paper. By the processes which have here been recommended, I have been enabled to obtain a similar view from the field of the microscope. (See Plates 10 and 12.) 5. The existence of oval, nucleated cells upon the Malpig- hian tuft of the higher animals has been clearly demonstrated by certain processes which, it is believed, are original. (See Plates 24, 25, and 26.) 6. Some facts and arguments adduced in this paper have led to the conclusion that the function of the Malpighian tuft is to separate from the blood many of the proximate elements of the urine in combination with water. 7. It is not improbable that any elements of the urine which may have escaped separation from the blood, while they were still in the Malpighian tuft, would pass on into the venous plexus, and, in combination with water, be separated from it by the epithelial cells of the uriniferous tubes. 8. The physiological views of Mr. Bowman, which have been so generally received, are not here adopted, and for rea- sons previously stated. 9. A mode of readily exhibiting the fibrous matrix of the kidney, and views of this structure in different animals have here been given. 434 Researches into the 10. The arrangement of the minute vessels as they pass through the substance of the matrix has been shown, and also the effect of its constriction upon the vessels in cases of indura- tion of the kidney. 11. The appearance of the matrix in this disease, and its effect upon the circulation, nutrition, and secretion of the organ. I am aware that the views expressed upon this point are not in accordance with those of some excellent pathologists. 12. The chemical and histological nature of the matrix. 13. With regard to the Plates, several views have been given, which may be regarded as new. They were all drawn from nature, with the exception of Plate 27, which was copied from the very excellent paper of Mr. Bowman in the Philoso- phical Transactions. The plates were drawn from the field of the microscope by Henry A. Daniels and Sicard David, ana- tomical draughtsmen of this city, whose services were the best that I could command. The greatest care was taken to insure accuracy in every instance. The woodcuts were made by Mr. Jacob Wells, 52 John Street, Mho is well known as one of the best engravers in this city. The microscopes employed were those of Nachet, of Paris, and of Powell and Lealand, of London. 14. In conclusion, it will be remembered, that the investi- gation of this subject was undertaken with the view of ascer- taining, if possible, the true structure of the kidney, and with the hope of thus, perhaps, settling the disputed points relative to its anatomy. Entering upon this examination without any preconceived theory, it has occupied much of my attention for some years past, and for the last twelve months I have labored upon the subject almost daily, sparing neither time, trouble, nor expense, and carefully guarding against arriving at any conclusion until after long continued and repeated examinations. The facts from which deductions have been drawn have all been obtained by the careful examination of the kidney in many animals, and especially in the frog, turtle, snake, alliga- tor, fish, bird, mouse, rat, squirrel, cat, dog, raccoon, rabbit, hog, sheep, deer, elk, moose, ox, horse, black bear, rhinoceros, mon- key, and in man. Among the important and disputed questions Structure and Physiology of the Kidney. 435 which have been considered, are those of the nature of the epi- thelium in the uriniferous tubes; of ciliary motion in the kidneys of the mammalia; of nucleated cells upon the Malpighian tuft; of the connection of that tuft with the uriniferous tube; of the function of the Malpighian tuft, and of that of the epithelial cells ; of the arrangement of the minute vessels of the kidney ; of the fibrous matrix—its nature and condition in health and disease. It now only remains for the better judgment of the Academy to decide whether these long-disputed points can now be regarded as satisfactorily determined. I take this opportunity of expressing my sincere thanks to the Academy for their kind and patient attention. 1 ~ -^ t