vein, which lies in front of the artery, and ends in the inferior vena cava (p. 474).

Nerves. The nerves which have been traced into the kidneys are small. They come immediately from the renal plexus and the lesser splanchnic nerve, and contain filaments derived from both the sympathetic and cerebrospinal systems. They may be traced accompanying the arteries to their finer branches, but it is uncertain how they end.

Intertubular Stroma.-Between the tubules and vessels of the kidney, although they are disposed closely together, a certain very small amount of interstitial matrix exists, first described by Goodsir, then by Bowman and others, and to which attention has latterly been paid by a number of observers, and especially by Beer. This matrix is for the most part nearly homogeneous, but has a more fibrous character in the vicinity of the ramifications of the bloodvessels. Fibres are likewise described by Ludwig and Zawarykin as passing round the Malpighian corpuscles, and others have been seen by Henle, coiling round the tubes of the medullary substance. The stroma is more abundant in the cortical substance than in the greater part of the medullary; but according to Henle it is very abundant towards the apices of the papillæ. Nuclei and connective tissue corpuscles are scattered through its substance. It is much more abundant in animals than in man, and in the human kidney it is more apparent in the young than in the adult, and is also much richer in corpuscles; in this respect resembling the connective tissue generally.

Absorbents.-The lymphatics of the kidney are numerous, consisting of a superficial set, and of deep lymphatics which issue from the hilus with the blood vessels. According to the researches of Ludwig and Zawarykin, the stroma of the kidney forms a thick network of freely intercommunicating lymphatic spaces, guided to the surface along the tissue round the bloodvesels. These spaces are similar to those previously found by Ludwig and Tomsa in the testicle, and held by His to possess epithelial walls. They are most abundant in the cortical substance.

Among writings on the kidney, the following may be here referred to:-Bowman, in Philos. Trans. 1842; Toynbee, in Medico-Chir. Trans. 1846; Gerlach, in Müller's Archiv, 1845; Johnson, article Ren, in Cyclopædia of Anat. and Phys.; Isaacs, in Trans. New York Acad. of Medicine, vol. i., 1857; Henle, Zur Anatomie der Niere, Göttingen, 1862, and in Handbuch; Ludwig and Zawarykin, in Wiener Kais. Acad. Sitzungsbericht, vol. xlviii. 1864; Chrzonszczewsky, in Virchow's Archiv, xxxi. 1864; Schweigger-Seidel, Die Niere des Menschen und der Saugethiere, Halle, 1865; Southey, in St. Bartholomew's Hosp. Reports, 1865; also, on the stroma, Goodsir, in Lond. and Edin. Journ. of Med. Science, May, 1842; and Beer, Die Bindesubstanz d. Menschlichen Niere, Berlin, 1859.

Development.-The development of the kidneys, and also that of the suprarenal capsules will be described later with that of the genito-urinary organs.

The Urine. This is a complex and somewhat variable fluid, containing in solution animal substances characterised by having a large amount of nitrogen in their composition, and derived, it would seem, from the waste of the tissues; also saline substances, and adventitious matters which have been introduced into the blood. The average quantity secreted daily is from 30 to 40 fluid ounces. Its specifie gravity varies in health from 1·015 to 1030, the average standard being 1·020. It is slightly acid in its reaction, and contains some mucus and epithelium. A thousand parts of ordinary urine usually contain 933 parts of water, and 67 of solid matter. The researches of Bowman upon the structure of the kidney in man and animals, render it probable that the solid urinary constituents are secreted by the tubuli, and that the watery part of the urine simply transudes through the vessels of the glomeruli.

The following analysis of the solid contents of the urine is from Lehmann, but it

THE URINE. THE SUPRARENAL BODIES.

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must be considered approximative only, since the proportion of the ingredients is liable to great variation in dependence upon food, exercise, and other conditions:—

Urea

49.68

Uric acid

1.61

Extractive matters, ammoniacal salts, and chloride of sodium

28.95

Among the extractive matters are kreatine, kreatinine, and hippuric acid.

SUPRARENAL BODIES.

The suprarenal bodies or capsules, or suprarenal glands, (capsula atrabilarice seu renes succenturiati of old anatomists), are two flattened bodies, each of which has a somewhat crescentic or bent triangular shape, and surmounts the corresponding kidney. The upper border, convex and thin, is often considerably elevated in the middle so as to form two sides of a triangle. The lower border is concave, and rests upon the anterior and inner part of the summit of the kidney, to which it is connected by loose areolar tissue it is thick, and almost always deeply grooved. The posterior surface rests upon the diaphragm. Its anterior surface is covered on the right side by the liver, and on the left by the pancreas and spleen it presents an irregular fissure named the hilus, from which the suprarenal vein emerges. The right capsule, like the right kidney, is placed lower down than the left. The suprarenal capsules vary in size in different individuals, and the left is usually somewhat narrower at its base, but longer from above downwards, and larger than the right. They measure from an inch and a quarter to an inch and three-quarters in height, and about an inch and a quarter in width; their thickness is from two to three lines. The weight of each in the adult is from one to two drachms.

:

Besides a covering of areolar tissue mixed frequently with much fat, the suprarenal capsules have a thin fibrous investment. Externally, they have a yellowish or brownish-yellow colour. When divided, they are seen tɔ consist of two substances: one, external or cortical, is of a deep yellow colour, firm and striated, and forms the principal mass of the organ; the other, internal or medullary, is in the adult of a dark brownish-black hue, and so soft and pulpy that some anatomists have erroneously described a cavity within it.

Its

The fibrous investment is so intimately connected with the deeper parts that it cannot be removed without lacerating the subjacent structure. deeper layers are destitute of elastic fibres, and are particularly rich in nuclei: they are continuous with the septa which enter into the formation of the substance of the organ.

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The cortical part of the suprarenal body, examined with a low magnifying power, is seen to consist of stroma, in which are imbedded columnar and reticulated masses measuring on an average th of an inch in diameter, arranged vertically to the surface of the organ, and containing cellular constituents. In the deepest part of the cortex, however, the colour is darker, and the columnar arrangement is lost, the stroma being more equally scattered; and immediately beneath the fibrous coat there is another very narrow layer in which the stroma forms oval spaces, of which it is difficult to say whether they communicate with the extremities of the columns or not. These inner and outer layers have been named by J. Arnold respectively zona reticularis and zona glomerulosa, while he applies the term

zona fasciculata to the main part; but as the transition from one of these parts to another is not sudden nor indicated by any line of demarcation, they

GROWN FETUS.

This figure shows the lobulated form of the foetal kidney r;, the renal artery and vein; u, the ureter; s, the suprarenal capsule, the letter is placed near the sulcus in which the large veins (') are seen dividing and dipping into the interior of the organ.

Fig. 662.-SECTIONS OF THE SUPRARENAL BODY.

A, Vertical section of the suprarenal body of a fœtus twice the natural size, showing the lower notch by which it rests on the summit of the kidney, and the anterior notch by which the veins penetrate, together with the distinction between the medullary and cortical substance.

B, longitudinal section of the cortical substance, showing the capsules containing nucleated cells and intervening blood vessels. 250 The figure represents a small fragment of a section made perpendicularly to the surface in a suprarenal body of which the blood vessels were partially injected. a, one of the superficial masses of cells (in the zona glomerulosa of J. Arnold); a', one of the longer masses slightly deeper (zona fasciculata); b, blood vessels running in the septa of connective tissue between the cell-masses in a part of the specimen; c, connective tissue and sheath substance on the surface; d, connective tissue of the septa: this figure, though true to nature in the representation of the scveral textures, is so far diagrammatic that the space occupied by the shorter masses of cells towards the surface is proportionally too small.

6000

3000

are probably only modifications of the same structure. The contents of the stroma consist of nucleus-like bodies from th to th of an inch in diameter, mixed with minute yellowish granules, and oily particles with granular matter adhering to them, together with large groups of closely-set nucleated cells containing granular matter and oily molecules. The cells vary from th toth of an inch in size, and their opposing sides are somewhat flattened, giving them the form of irregular polyhedra: the larger cells are most loaded with oil globules. In many instances probably the appearance of free nuclei and oil globules is to be explained by cell-walls being ruptured or remaining unrecognised.

1 2000

MINUTE STRUCTURE OF SUPRARENAL BODIES.

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According to Simon the columns consist of distinct tubes with a limiting membrane; Ecker and others affirm that no continuous tubular cavities exist, but that rows of closed vesicles, many of them oval in shape, and over-lapping each other, are placed in such manner as to resemble tubes; while Gray believes that the walls of adjoining vesicles are sometimes removed by absorption, so that tubular cavities are formed by the coalescence of neighbouring vesicles. Kölliker, however, and other observers, maintain with more correctness, that the so-called vesicles are merely loculi or cavities in the stroma of the organ, possessing no distinct limitary membrane, and producing the appearance of a tubular structure by their apposition in linear series. The small arteries, entering from the surface, run parallel to these columns, frequently anastomose together between them, and surround each row of vesicles with a fine capillary network. Small bundles of nerves pass inwards in the septa between the columns to reach the medullary part of the organ, and their fibres begin to spread out in the zona reticularis, but do not appear to be distributed to the cortical substance.

The medullary part of the suprarenal capsule is separated from the cortical part by a layer of connective tissue, the fibres of which are parallel to the two parts, and allow them to be easily separated one from the other in sections prepared for the microscope. In the thinner parts of the adult organ there is no medullary part, or it has shrunk away, and the layer of connective tissue referred to is found separating the deep surfaces of two opposed portions of the cortical part; but in the young state the distinction of cortical and medullary probably extends throughout the whole. The medullary part is traversed in the centre by venous trunks, which receive the whole of the blood which has passed through the organ. The stroma is delicate, arranged in a reticular manner; the pulpy substance which lies in it is difficult of examination, but consists of cells, differing from those of the cortex in being destitute of oil globules, and some of them branched. The bundles of nerves which pass through the cortical substance run between it and the medullary substance, and then form a copious interlacement which extends through the whole of the medullary stroma. According to Leidig and Luschka, the cells of the medullary substance are ganglionic; and Luschka states that he has found them both connected one with another and with nerve fibres; but this view still requires confirmation. Moers, while he denies that the cells of the medullary parenchyma are nervous, describes ganglia on the nerves where their bundles begin to break up. The medullary substance receives its blood by the continuation inwards of the capillary network of the cortex, the blood from which is collected by venous radicles which open into the stems in the centre of the organ.

Vessels. The suprarenal bodies receive arteries from three sources, viz., from the aorta, the phrenic, and the renal arteries. The distribution of their capillary vessels has already been mentioned.

The veins, which pass out from the centre, are usually united into one for each organ. The right vein enters the vena cava inferior immediately, whilst the left, after a longer course, terminates in the left renal vein.

The lymphatics are imperfectly known. Kölliker has seen a few small trunks upon the surface; and Luschka has, in addition, observed others emerging from the interior in company with the vein.

Nerves.-The nerves are exceedingly numerous. They are derived from the solar plexus of the sympathetic, and from the renal plexuses. According to Bergmann, some filaments come from the phrenic and pneumogastric nerves. They are made up mainly of dark-bordered white fibres, of different sizes, and they have many small

ganglia upon them before entering the organ. The nerves are especially numerous in the lower half, and inner border.

Accessory suprarenal capsules are occasionally met with, attached by connective tissue to the main bodies; and varying from a small size up to that of a pea. According to Duckworth, they possess no medullary part.

On the subject of the suprarenal capsules may be consulted,-Ecker, Der feinere Bau der Nebennieren, Braunschweig, 1846; Simon on the Thymus Gland; Frey, article Suprarenal Capsules," in Cyclop. of Anat. and Phys.; Harley, in the Lancet, June, 1858; Duckworth, in St. Bartholomew's Hosp. Reports, 1865; Moers, in Virchow's Archiv, 1864, vol. xxix. p. 336; J. Arnold, Virchow's Archiv, 1866, vol. xxxv. p. 64; Leidig, Kölliker, Luschka, and Henle, in their Handbooks.

Function.-Nothing is known positively with regard to the functions of the suprarenal capsules. The opinion which has met with most acceptance among physiologists is that these bodies belong to the class of blood-vascular glands, and exert some influence upon the elaboration or disintegration of nutritive material. Bergmann, however, who was the first to point out the richness of their nervous supply, suggested that they were parts of the sympathetic nervous system, and in this opinion he has been followed by Leidig and Luschka; while Kölliker states that, upon anatomical grounds, he is inclined to consider the cortical and medullary portions as functionally different; former belonging to the group of vascular or ductless glands, the latter appearing to be an apparatus appertaining to the nervous system. Brown-Séquard found that injuries to the spinal cord in its dorsal region produced congestion and subsequent hypertrophy of the suprarenal bodies. Addison has shown that a bronzed tint of skin, together with progressive emaciation and loss of strength, is to be found in conjunction with various forms of disease more or less involving and altering the structure

of these bodies.

the

THE URETERS.

The ureters are two tubes which conduct the urine from the kidneys into the bladder. The upper, dilated, funnel-shaped commencement of each in the pelvis of the kidney, into which the calyces pour their contents, has already been described. Towards the lower part of the hilus of the kidney the pelvis becomes gradually contracted, and opposite the lower end of the gland, assuming the cylindrical form, receives the name of ureter. extend downwards to the posterior and under part or base of the bladder, into which they open, after passing obliquely through its coats.

These tubes

The ureters measure from fourteen to sixteen inches in length, and their ordinary width is about that of a goose-quill. They are frequently, however, dilated at intervals, especially near their lower end. The narrowest part of the tube, excepting its orifice, is that contained in the walls of the

bladder.

Each ureter passes, at first, obliquely downwards and inwards, to enter the cavity of the true pelvis, and then curves forwards, and inwards, to reach the side and base of the bladder. In its whole course, it lies close behind the peritoneum, and is connected to neighbouring parts by loose areolar tissue. Superiorly, it rests upon the psoas muscle, and is crossed, very obliquely from within outwards, below the middle of the psoas, by the spermatic vessels, which descend in front of it. The right ureter is close to the inferior vena cava. Lower down, the ureter passes over the common iliac, or the external iliac vessels, behind the termination of the ileum on the right side and the sigmoid flexure of the colon on the left. Descending into the pelvis, it enters the fold of peritoneum forming the corresponding posterior false ligament of the bladder, and reaching the side of the bladder near the base, runs downwards and forwards in contact with it, below the obliterated hypogastric artery, and is crossed upon its inner side, in the male,