A treatise on Bright's disease and diabetes with especial reference to pathology and therapeutics

Front matter

A TREATISE

ON

BRIGHT'S DISEASE AND DIABETES.

Preface

It is quite usual for authors, in their prefaces, to give some reason for having written the book which they thus introduce, — in a word, to apologize for its appearance. In the present instance the existence of excellent treatises on both subjects covered by the title, make it more than usually difficult to justify the appearance of another. The writer can only say that, for more than fifteen years, his thoughts, his studies, and his practical work have all been in the direction suggested by these subjects, and that during that time material has passed under his observation which ought at least, if properly used, to have resulted in an experience which should be useful to others. Whether this has been the case or not, must be left to the decision of those who may first read or examine the work.

In carrying out his object, the author has necessarily, in order to insure completeness, availed himself of the work of others, as well as his own, endeavoring, however, in all instances, to give credit where credit is due, and if he has omitted any proper acknowledgment it has been entirely unintentional. In the section on the " Histology of the Kidney," while he has used the illustrations of other writers, he has also added a number of original drawings, from the careful pencil of Dr. George C. Piersol. It is thought they will add to the accurate knowledge of the subject.

xii

PREFACE.

The very wide difference in the nature and pathology of the two sets of diseases, has not been overlooked in including them under the same cover ; but when it is remembered that although diabetes is not a urinary disease, it is nevertheless a disease to a knowledge of which a study of the urine is indispensable, and that one who devotes himself to the latter must inevitably be brought into frequent and intimate contact with diabetes, it is but natural that the consideration of the two conditions should be united.

1506, Spruce Street, April 1st, 1881.

Table Of Contents

BEIGHT'S DISEASE.

SECTION PAGE

I. Structure of the Kidney, 17

Section I. Structure Of The Kidney

The few facts in the coarser anatomy of the kidney which it is necessary to recall with a view to a correct understanding of its diseases, are, before section of the organ, its size, weight, color, consistency, and the relation of its capsule to its substance; after section, the appearance of the cortex or convoluted portion, as contrasted with the pyramids of straight tubes in the medulla, and the relative area of each.

As to size and weight, the adult kidney is usually about 11 centimeters (4.4 inches) in length, 5 centimeters (2 inches) wide, and .75 centimeter (.3 inch) in thickness. It weighs in the male 113.5 to 170 grams (4 to 6 ounces); female, a little less, 113.5 to 156 grams (4 to 5| ounces). Its color in health is dark red, surface smooth, and in consistence it is usually firm and slightly elastic. The capsule is easily stripped off from the substance of the organ, dragging none of the proper glandular structure with it.

On section of the kidney the cortex is found to be granular in appearance, and uniformly light-red in color. It varies somewhat in width, but is usually 5 to 6 millimeters (I to \ inch) wide, and in longitudinal section is seen to dip down between the pyramids of the medulla. These pyramids, ten to fifteen in number, are striated or fibrous in appearance, uniformly dark-red, and terminate in as many papillae in the pelvis of the organ.

brigiit's disease.

More important to a correct understanding of the pathology of kidney diseases is a knowledge of the minute structure of the organ. Even the naked eye can discover further differences on the surface of a longitudinal section of the kidney, such as is

Fio. 1.

Longitudinal section through the kidney, the pelvis of the kidney, and a number of renal calyces. A, branch of the renal artery; U, ureter; C, renal calyx; 1, cortex; 1', medullary rays; 1", labyrinth, or cortex proper; 2, medulla; 2', papillary portimi of medulla, or medulla proper; 2", border layer of the medulla; A, 3, transverse section through the axes of the tubules of the border layer ; 4, fat of the renal sinus; 5, 5, arterial branches ; * transversely coursing medullary rays. — After ELenle,

pi'esented in Fig. 1 ; and these differences are rendered still more striking if the bloodvessels are injected with a coloring matter. From each papilla as a centre radiate the excreting tubules, which appear as dark-red .stritc in the natural organ. For a

STRUCTURE OF THE KIDNEY.

short distance they remain in contact, forming a continuous surface, known as the papillary portion of the medulla (Ludwig), or the medulla proper (Henle). This is represented at

Fig. ?. FlG- 3-

Fig. 2. — Partially diagrammatic sketch of the structure of the kidney in longitudinal section, and, Fig. 3, Tangential section through the cortex; bloodvessels injected. Alter Eiudtleisch and Ludwig, modified, k, papillary layer; i, border layer ; A, cortex. The lighter striffi, PF, are bundles of uriniferous tubules, a part of which are seen prolonged into the cortex as medullary rays or pyramids of Ferrein. Between each two of these in the cortex is the renal labyrinth, or secreting portion proper of tho kidney. a, a, a, embrace the bases of the renal lobules, which, in transverse section at Fig. 3, appear as polygonal figures. RA, a larger branch of the renal artery, which separates the medulla from the cortex ; 11V, lumen of a renal vein which takes up the interfascicular vessels ; t be latter appear in transverse sections on the surface as stellate figures ; VR, straight vessels {wua recta) ; PA, surface of a renal papilla.

Fig. 3. — Polygonal appearance of the lobuli when cut transversely. F, transverse sections of the tubules forming the pyramids of Ferrein.

2', Fig. 1, and at h, Fig. 2. As they proceed towards the periphery, the stria? become separated into bands of nearly equal width, between which are collections of other striae. These in bright's disease.

an injected kidney exhibit the color of the injecting fluid, but in an uniujected organ, though lighter or less opaque, are scarcely distinguishable from the bundles of straight tubes with which they alternate, unless they happen to be filled with blood. These striae are, therefore, bloodvessels, and the portion of the medulla which is thus made up of alternate bands of bloodvessels and straight tubules is called the boundary layer, or marginal layer of the medulla (2", Fig. 1, and i, Fig. 2). Close examination, especially with a low magnifying power, enables us to trace into the cortex almost to its border the bundles of striae or straight tubes which come from the papillae (1', Fig. 1, and PF, Fig. 2). In this situation they are called medullary rays, or pyramids of Ferrein. Alternating with these medullary rays in the cortex is a granular portion, yellowish-red in the uninjected organ, which is the renal labyrinth, or cortex -proper.

The further study of the minute structure is best facilitated by a separate consideration of the tubules, bloodvessels, and connective tissue elements, and the lymphatic and nervous elements which accompany them.

I. The Uriniferous Tubules.

These, with the bloodvessels, make up the great bulk of the organ. They may be studied from their beginnings in the cortex, or backwards as it were, from their terminations in the discharging-tubes on the papillae. Selecting the former, the little granules visible to the naked eye in the labyrinth are the beginnings of the uriniferous tubules. These are spherical dilatations, .15 to .2 mm. (T£0 toT|g inch) in diameter, formed of basement membrane lined by a mosaic of pavement epithelium. They are the so-called Malpighian capsidcs (1), Fig. 4, and are continuous, by a necklike construction (2), with the proximal convoluted tubule (3), which winds towards the adjacent medullary ray; reaching which, it passes vertically downward as the spiral tube (4) of Schachowa. These portions are all in the cortex, A. At the juuction of the cortex and the border layer, the spiral tubule becomes suddenly nar-

STRUCTURE OF THE KIDNEY.

rower, and dips down through this layer, B, as the descending limb (fj) of Ilenlo's loop, the loop itself (G) being formed in the

Fig. 4

Diagrammatic representation of the course of two urinary tubules.-After Jvlkix and

Noble Smith.

papillary layer, C. Re-entering the boundary layer, the tube becomes suddenly enlarged and slightly wavy in its course, forming "the first thick portion" (7) of the ascending limb of bright's disease.

Henle's loop. At the middle of the boundary layer it again becomes narrower and spiral in its course, forming the "spiral part" (8) of the ascending limb. The ascending limb now re-enters the cortex in the medullary ray, again becoming narrower, though not of uniform diameter, and straighter, but still slightly wavy in its course (9). Sooner or later, after re-entering the cortex, the tubule dips away from the medullary ray and passes into the labyrinth as a tube irregular in outline, breadth, and course, whence it is called the irregular tubule (10). Fairly in the labyrinth, it again becomes wider and convoluted, forming the intermediary segment (Schaltstuck) of Schweigger-Seidel, or distal convoluted tubule (11). Finally, by an archlike turn, whose convexity is towards the circumference of the kidney, it passes back towards the medullary ray as a narrower "curved part" (12) of the collecting-tube, which, uniting •with other similar tubules, forms the "straight part" (13) of the collecting-tube in the cortex. The collecting-tube passes down, still as a straight tube (14), though growing gradually wider, through the boundary layer. In the papillary layer it becomes the large collecting-tube, or tube of Bellini, which, uniting with others, forms the " ducts " or " discharging-tubes " which open on the papilla.

In its course from its commencement in the Malpighian capsule to its termination in the collecting-tube the uriniferous tubule changes its diameter many times. First, there is the constriction at the neck of the capsule, which is less than one-half the diameter of the convoluted portion immediately succeeding it, and of which the average width, in the adult, is about .06 mm. (^ inch), and in the newborn child, about .016 mm. (yg^ inch). The third change is found in the narrowing as the tubule becomes the descending limb of the loop of Henle. The fourth is the slight dilatation just before or after the loop is formed. Fifth, a slight temporary narrowing at the " spiral part" of the ascending limb. Sixth, a further narrowing as the ascending limb re-enters the cortex. Seventh, the numerous changes in the irregular tubule (10). Eighth, the widening of the intermediary portion, of which the diame-

STRUCTURE OF THE KIDNEY.

ter about equals that of the convoluted tubule. And, ninth, a constriction as the latter terminates in the collecting-tube.

After the collecting-tube is formed it receives, just below its summit, a few additional canals, and then passes singly down to the papillary part of the medulla. Its diameter in the medullary ray is between .04 mm. (a£5 inch) and .08 mm. (,J2 inch) in the adult, and in the child .008 (, f„ inch) and .05 mm.

Fig. 5.

Diagrammatic exposition of the method in which the uriniferous tubes unite to form primitive cones. — After Ludwig.

(jto~o~ incn)> the narrowest canals being in the centre of the ray. Having reached the papillary portion, the collecting-tubes unite by twos ; first those of a single medullary ray, forming the principal or excreting tubes; then these unite with other excreting-tubes to form the papillary ducts, of which fifteen to twenty open on the surface of each papilla into the pelvis of the kidney.

Dr. George H. Rose, in an able graduation thesis On the Arrangement of the Uriniferous Tubules, presented to the Medical Faculty of the University of Pennsylvania, in March, 1879, concluded, first, that not all of the tubuli uriniferi go to form loops of Henle ; second, that the medullary rays are bright's disease.

made up of the convoluted tubes which clo not form loops, as well as the collecting-tubes and ascending and descending limbs of Henle.*

Structure of the Uriniferous Tubules. — The Malpighian capsule is composed only of the basement membrane and mosaic of epithelial squaras to which allusion has already been made. The cells, as seen in nitrate of silver preparations, are relatively large, although not uniform in size, and are provided with round and oval nuclei. The nuclei are arranged in groups of from two to ten. The group nuclei are round, about .01 mm. (0500- inch) i» diameter, and, though flat, project slightly into the cavity of the capsule {d, Fig. 15). Each is surrounded by an amount of protoplasm, which is smaller the greater the number of nuclei in a group, whence the varying size of the cells. In the young kidney these cells are less flattened, and the nuclei project still further into the cavity of the capsule, as is seen in Fig. 15.

The capsules thus formed surround the capillary ball or glomerulus presently to be described, forming with it the Malpighian co7yusde. The latter are encircled by a few concentric layers of connective tissue, which are most numerous about those nearest the medulla. (See Fig. 15.)

This single layer of cells lining the capsule, which is comparable to an endothelium rather than an epithelium, extends into the neck of the capsule, whence onward to the papillary portion of the medulla the uriniferous tubule is composed of a basement membrane lined with an epithelium. The basement membrane contains an occasional nucleus, and in nitrate of silver preparations tlfe convoluted tubules may be imperfectly mapped off into endothelial plates like the walls of blood and lymph vessels similarly treated ; but the membrane is otherwise quite glasslike, affording, when the epithelium is washed out, one of the most satisfactory and typical examples of a homogeneous membrane.

* Dr. Rose's studies were made with extreme care upon macerated preparations of the kidney. They were many limes repeated, and his thesis received the award of a prize.

STRUCTURE OF THE KIDNEY.

The epithelium below the neck varies greatly, although it is everywhere single-layered and nucleated. The nucleus, alone, of the various cells is quite uniform, being round, sharply defined, and slightly granular. On the other hand, in the convoluted part of the tubule, the protoplasm of the adjacent cells is not differentiated, but each cell fuses, as it were, into its neighbor, so that the lining of the tubes, especially when acted upon by acetic acid, presents the appearance of a nucleated protoplasm rather than of a number of separate nucleated cells. At intervals may be observed, however, more especially if the tubules have been injected, certain

Section through the cortex of a fresh kidney, showing cloudy epithelium. The spheroidal nuclei are concealed. In the wider tubules irregular, in the narrower, regular fissures divide the epithelial mass. After Ludwig.

clefts or fissures where the cell bodies are not thus completely fused. These are well shown in Fig. 6, from Ludwig. According to Klein, the clefts are occupied by minute septules, containing here and there an oblong or angular nucleus, which pass in from the basement membrane. Of importance in connection with the study of diseases of the tubules is the fact that, in this portion, the epithelium is but loosely attached to the basement membrane, and may even be pressed out in the shape of a solid epithelial cylinder, or left as such by retraction of the basement membrane. The protoplasm of the cells bright's disease.

in this situation is more or less "cloudy" in health, from the presence of a number of dark granules of albuminous composition, and even of some minute fat-globules. These serve to render the nucleus more or less obscure, while the addition of acetic acid, dissolving the albuminous granules, renders it again distinct.

E. Heidenhain* adds to the structures as above described an

Fig. 7. Fig, 8. Fig. 9.

Fig. 7. — Transverse section through a convoluted tubule of a fresh dog's kidney, without the addition of any fluid. Hartnack imm. ix, tube in, drawing prism. Magnified 500 diameters.'-After Heidenhain.

Fig. 8. — Section of a convoluted tubule of a dog's kidney, ammonium chromate preparation. Hartnack Obj. vii. Drawing prism, tube out. Magnified 440 diameters. — After Heidenhain.

Fig. 9. — Surface view of a convoluted tubule. Same treatment and amplification. — After Heidenhain.

additional element, the effect of which is, as he says, to make the epithelial cell of the convoluted tubules a very complicated organized structure. According to him the protoplasm is further differentiated into a large number of delicate cylindrical structures, which he calls " rodlets " (Stabchen). These, rest-

* R. Heidenhain, Mikroskopische Beitriige zur Anatomie unci Physiologie der Nieren, in Max Schultze's Archiv fur Mikroskopische Anatomie. Bd. x, 1874, s. 1.

STRUCTURE OF THE KIDNEY.

ing their peripheral ends on the basement membrane, perforate the epithelial layer in a radiated manner, imbedded in a very small quantity of formless matrix. The rodlets envelop, " like a mantel," the nuclei, which are placed at regular intervals, surrounded by a considerable remnant of undifferentiated protoplasm. According to Heidenhain the minute granules, for-

Fig. 10— Isolatod cells and rodlets from the rat's kidney. Same treatment and amplification.— After Heidenhain.

Fig. 11. — An isolated fragment of a descpnding limb, showing the clear, delicate epithelium, with alternate projections caused by the nucleus. — After Ludwig.

Fig. 12. — Ascending limb of loop, showing imbricated arrangement of columnar cells, according to Ludwig.

Fio. 13 — a, a portion of a convoluted tubule; b, of an ascending limb of Henle's loop, according to Heidenhain. The ascending limb has the greater lumen. Klein confirms Heidenhain in all essential particulars, but says, also, that, in the narrow part of the ascending limb, about the middle of the boundary layer, " many cells appear possessed of short processes and are more or less imbricated, a fact already known to Steudeuer."

merly described as present in the matrix of the cells, are nothing but the transverse sections of the rodlets.

Figs. 7, 8, and 9, from Heidenhain's paper, exhibit the appearances described.

Dr. Klein, of London, substantially confirms the observations of Heidenhain, but says these rods or fibrils, when looked at from the surface, are clearly connected into a network, so that they are more probably "septa of a honeycombed network brigiit's disease.

seen in profile." In the Atlas of Histology, part xi, Fig. 1, recently issued by Dr. Klein, in connection with Mr. E. Noble Smith, this peculiarity in the structure of the epithelium is exquisitely brought out.

In the narrow descending limb of Henle's loop is found a single layer of epithelium, the cells of which are characterized by a transparent protoplasm and oval nucleus, which projects into the lumen of the tubule at alternate points, as shown in Fig. 11. The resemblance of these tubules to capillary bloodvessels is very marked, especially in transverse section ; but, as Klein points out, the nuclei are more numerous than in a capillary, and the tubule has, further, a membrana propria outside the layer of cell-plates.

In the ascending limb of the loop, where the diameter again becomes greater, Ludwig describes the epithelial cells as columnar, arranged in an imbricated manner, and distinctly differ-

Irregular tubule from the cortex of the kidney of a dog. — After Klein.

entiated by a cleft about half way between two nuclei, as in Fig. 12. But according to Heidenhain's investigations, the epithelium of this broader ascending limb agrees essentially with that of the convoluted portion of the tube, the rodlets being similarly developed, as shown in Fig. 13. It is, however, tolerably easily distinguished from the convoluted tubule by the fact that the lumen of the latter is much narrower in consequence of the greater thickness of its cells, which, therefore, encroach more upon its lumen.

The irregular tubule, as figured by Klein, Fig. 14, is a striking object. He describes it as follows :

" It is situated among the convoluted tubes of all parts of the labyrinth ; it has a very irregular and angular outline; in some places three and four times as thick as in others, and then

STRUCTURE OF THE KIDNEY.

of almost the same breadth as a convoluted tubule. But this greater thickness is due merely to a greater thickness of the lining epithelial cells, the lumen remaining everywhere a narrow canal. The cells show, in the profile view, exceedingly thick rods of a bright, homogeneous aspect, more distinct than in any other section of the urinary tubule. The cells are very angular and, in many places, imbricated ; but in this, as in the former cases, this imbrication is due to the irregular outline of the tube and the great variation in height of the adjacent cells. Each cell possesses an oval or angular nucleus next the lumen."

In the intermediary portions the epithelium reassumes the appearance of that of the convoluted segment of the tubule ; and here, again, Heidenhain and Klein reintroduce the rodlets, or, rather, their ends, as the cause of the faintly granular appearance.

In the collecting-tubes the epithelium is described as columnar, but the cells are more nearly cubical ; they are sharply defined, rather broader at the base, which is seated on the wall of the tubule, while their truncated apices are directed towards its lumen. In the smaller canals, which unite in the medullary rays to form larger tubes, the round nuclei are surrounded with but a small amount of protoplasm. In the larger tubes the protoplasm is more abundant and the nuclei about the same size as in the smaller. Isolated cells from both regions exhibit projections and prolongations of protoplasm, so that it is really only in transverse sections of the collecting- tubes that the columnar or cubical appearance of the cells is maintained. In the papillary ducts a basement membrane can no longer be differentiated from the connective tissue around it, and the cells, Avhich are here more elongated and typically columnar, rest upon the connective tissue alone.

Heidenhain says that, in the primary branches of the collecting-tubes, he has, here and there, observed that the so-called cylindrical cells are placed in an oblique manner, so as to give an imbricated appearance, and suggests that this may have given rise to the view of Ludwig, already described in these pages, that the ascending broad limb of ITenle's loop is thus lined.

BRIQHI'S DISEASE.

Anatomical Peculiarities of the Glomerulus or Malpighian Tuft; its Epithelial Covering, etc. — It is now generally conceded that, in addition to the mosaic of epithelium which lines the Malpighian capsule, the glomerulus itself is covered with a layer of epithelial cells, but all observers are not agreed as to its exact arrangement. According to some it simply covers the surface, bridging the space between the capillaries and the lobules which compose the glomerulus. Others consider that it also clips down between the capillary loops. The studies of Heidenhain* and of Langhans,f which are among the most recent, lead them to accept the latter view, while Schweigger- SeidelJ and Von Seng§ adopt the former. The cells are for the most part well defined, but differ somewhat according as they cover the surface of the glomerulus or dip down between the capillary loops. In the former instance they are thin vaulted plates, whose concave surface rests upon the convexity of the capillary loop and is moulded to it. The shape of the cells also varies somewhat, according as they cover one or more capillary loops. In the latter instance the under surface of the cell is divided by projecting edges into several concave areas for the reception of the individual capillary loops. The edges unite at the centre, at which is the nucleus, which itself is conical in shape. At this situation — the seat of the nucleus — the external or upper surface is frequently depressed, so that the lateral extensions of the cell assume a pterygoid appearance. Other cells are concave on both surfaces, an effect probably due to their being insinuated between two capillary loops.

The nuclei measured by Langhaus are oval, .01-.014 mm.

(aB'ou-rVsff in-) long and -006-.01 mm. (^gg-^Vir iu0 wide> and somewhat flattened. The cells themselves reach .025 mm.

* Heidenhain, Archiv fur Mikrosk. Anatomie, B. x, 1874, p. 3.

f Langhans, Ueber die Veriinderungen der Glomeruli bei der Nephritis nebst einigen Bemerkungen iiber die Entstehung der Fibrincylinder. VirchcVs Archiv, 76 Bd., erstes Heft, April, 1879, p. 85.

J Schweigger-Seidel, Die Nieren, Halle, 1865, p. 76.

\ Victor von Seng, Ein Beitrag zur Lehre von den Malpighischen Korperchen der Menselilichen Nieren. Wiener Sitzungsberichte, lxiv, 13 April, 1871.

*

STRUCTURE OP THE KIDNEY.

(toVo m-) *n diameter at a maximum. In some instances the line of junction between neighboring cells is not demonstrable, so that the covering of the glomerulus appears as a homogeneous nucleated plate. The cells and nuclei are much more easily demonstrable in the foetal kidney, in which they are more cubical, as seen in Fig, 15, from Klein's Atlas ; undergoing a change after birth which is compared by Schweigger-Seidel to the post-foetal transformation of the alveolar epithelium of the lung. The epithelial covering of the glomerule is continuous with the epithelial lining of the capsule, as is well shown in Fig. 15.

According to Axel Key the capillary bloodvessels of the lobules of the glomerules are held together by a homogeneous connective tissue containing flattened stellate and nucleated connective tissue corpuscles. But Langhans was unable to convince himself of the presence of connective tissue, except the adventitia of the vas afferens, which extends only until the vessel begins to break up into capillaries.

The capillaries of the glomerule or Malpighian tuft, like all capillaries, are provided with nuclei, which in common with brigiit's disease.

all the cellular elements named are subject to pathological change.

There are no Malpighian corpuscles in that part of the cortex immediately bordering the capsule, nor in that bordering the boundary layers, that is, in the most external and most internal portions. See a and a, Fig. 4.

II. The Bloodvessels of the Kidney.

The renal artery, before it enters the substance of the organ,

Fig. 1G.

A

Distribution of the larger bloodvessels of the kidney. Engraved from a photograph of an injected and macerated preparation by Hyrtl in the Museum of the College of Physicians, Philadelphia. A, the artery. B, B, B, B correspond to the distinct lobar divisions of the kidney, to each one of which (be branches of an artery are distributed, which again unite to form the area of the cortex. The open spaces correspond to the areas of the straight tubules or pyramids, which containing comparatively few bloodvessels were washed away in the maceration. The vertical interlobular arteries alluded to in the text arc not seen, because the kidney is shown eutire and not in heuii-sectiou.

breaks up into two or three branches, which penetrate the capsule at the border of the pelvis of the kidney, and, after further rapid subdivision, radiate directly to the upper part of the marginal layer of the medulla. From branches arching more or less irregularly along this border ascend vertical branches.

STRUCTURE OF THE KIDNEY.

These pass into the labyrinth midway between two medullary rays, and are called interlobular or interfascicular arteries. From them pass off, laterally, numerous smaller branches called afferent,— vasa afferentia,— each one of which promptly perforates the nearest Malpighian capsule at a point opposite to the constricted neck of the latter. The vas afferens, according to the measurements of Thoma,* is .014 to .02 mm. (T1>„ to „fo inch) in diameter. Having perforated the capsule, it immediately splits up, forming a capillary ball— the Malpighian tuft or ghmerule. The capillary vessels of this ball reunite within the

Diagrammatic representation of the bloodvessels in the cortex of the kidney, m, region of the medullary ray ; 6, region of the tortuous portion of the tubules ; AI, interlobular artery ; VI, interlobular vein ; VA, vas afferens glomeruli ; VE, vas efferens; GL, Malpighian capsule containing iu its interiorthe capillary ball known as the glomerule, or Malpighian tuft ; VZ, venous twig of the interlobular vein. — After Ludwig.

capsule to form a vessel, — the fas efferens, — which perforates the capsule outwards at the same point at which the vas afferens enters, and slightly exceeds the latter in diameter. The efferent vessel proceeds towards the nearest medullary ray, and becomes a second time capillary. The resulting network embraces partly the straight tubules of the medullary ray, and partly the tortuous tubules, and, in the extreme periphery of the cortex, to which the medullary rays do not extend, the tortuous

* Thoma, Zur Kenntniss der Circulationstorung in deri Nieren bei chronischer interstitieller Nephritis. Virchow's Archiv, Bd. 71, 1877. s. Go.

brigut's disease.

tubules only. To these capillaries are added others, derived from a few minute branches given off by the afferent vessels va

Diagram of the circulation In the kidney.— After Ludwig.

before they reach the Malpighian capsule. A few only of the va8a efferentia lying adjacent to the medulla do not thus divide, but distribute their branches in a manner presently to be described. With these exceptions, the capillaries from all the neighboring efferent vessels communicate with each other, and the whole cortex becomes interpenetrated, as is well shown in Figs. 16 and 18. The meshes of the resulting network surrounding the convoluted tubules are small and nearly round, while those embracing the medullary rays are larger and wider. According to Ludwig, the vessels are not closely applied to the tubules, but lacuniform spaces, frequently filled with fluid, intervene between the two. The terminal branches of the interlobular arteries reach the capsule of the kidney.