Malpighian tubule

“ The position of the legs in relation to the other parts of the body is peculiar to the dragon-flies; the legs seem to be unfit for walking, the Insects never using them for that purpose.
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Several peculiarities in the internal anatomy deserve notice. The alimentary canal in Libellula is about as long as the body, the oesophagus and chylific stomach being elongate, while the intestine is short and divided into only two parts; there is no definite proventriculus. The Malpighian tubules are shorter than usual; they are about forty in number. The male has no vesiculae seminales ”

“ In some cases they are budded off from the hind-gut of the embryo when this is still very small; in other cases they appear later; frequently their number is greater in the adult than it is in the young. In Gryllotalpa there is one tube or duct with a considerable number of finer tubes at the end of it. There is no muscular layer in the Malpighian tubes, they being lined with cells which leave a free canal in the centre. The tubes are now thought, on considerable evidence, to be organs for the excretion of uric acid or urates, but it is not known how they are emptied. ”

“ In the male the anterior segmental tubes, which even in the embryo exhibit signs of atrophy, become in the adult completely aborted (as has been already shewn by Semper) , and remain as irregular tubes closed at both ends, which for the most part do not extend beyond the Wolffian duct (Pl. 20, fig. 4, r.st) . In the adult, the first two or three segments with these aborted tubes contain only accessory Malpighian bodies; the remaining segments, with aborted segmental tubes, both secondary and primary Malpighian bodies. In neither case are the Malpighian bodies connected with the aborted tubes. ”

“ They are present for a considerable portion of the body cavity, extending backwards from a point shortly behind the pronephros. They soon separate from the peritoneal epithelium, become hollowed out into canals, and join the segmental duct. At their blind extremity (that originally connected with the peritoneal epithelium) a Malpighian body is formed.
The pronephros is only a provisional excretory organ, the atrophy of which commences during larval life, and is nearly completed when the Ammocœte has reached 180 mm. ”

“ Fig. 5. Part of the Wolffian body of a nearly ripe male embryo of Scyllium canicula as a transparent object. Zeiss a a, ocul. 3. The figure shews two segmental tubes opening into the body-cavity and connected with a primary Malpighian body, and also, by a fibrous connection, with a secondary Malpighian body of the preceding segment. It also shews one segmental tube (rst) imperfectly connected with the accessory Malpighian body of the preceding segment of the kidney. The coils of the kidney are represented somewhat diagrammatically. ”

“ In the large white kidneys there is much variety. In some of them one is surprised to find how slight the minute lesions are. In others the principal changes are in the epithelium of the tubes, so that it may be difficult to tell whether they are examples of parenchymatous or of diffuse nephritis. In many others there is a very marked production of new connective tissue either in patches or diffuse. The large white kidneys which are waxy differ from the others only in the addition of the waxy degeneration of the Malpighian tufts and arteries to the other lesions. ”

“ At the junction of the median with the intermediate portion, and therefore at the neck of the Malpighian body, a canal grows out in a ventral direction, which meets the [Pg 709] peritoneal epithelium, and then develops a funnel-shaped opening into the body cavity, which subsequently becomes ciliated. In this way the peritoneal funnels which are present in the adult are established. ”

“ The segmental tubes which form it are stated by Fürbringer to arise from solid ingrowths of peritoneal epithelium, developed successively from before backwards, but Sedgwick informs me that they arise as differentiations of the mesoblastic cells near the peritoneal epithelium. They soon become hollow, and unite with the segmental duct. Malpighian bodies are developed on their median portions. They grow very greatly in length, and become much convoluted, but the details of this process have not been followed out. ”

“ Structure of the Kidneys. The pelvis is surrounded by reddish cones, about twelve in number, projecting into it, called the pyramids of Malpighi. The apices of these cones, known as the papillæ, are crowded with minute openings, the mouths of the uriniferous tubules, which form the substance of the kidney. These lie parallel in the medullary or central structure, but On reaching the cortical or outer layer, they wind about and interlace, ending, at last, in dilated closed sacs called Malpighian capsules. ”

“ According to Braun the segmental cords in Reptilia are buds from the outer walls of the Malpighian bodies. The bud from each Malpighian body grows into the genital ridge before the period of sexual differentiation, and sends out processes backwards and forwards, which unite with the buds from the other Malpighian bodies. There is thus formed a kind of trabecular work of tissue in the stroma of the ovary, which in the Lacertilia comes into connection with the germinal epithelium in both sexes, but in Ophidia in the male only. ”

“ Albuminous material, the source and nature of which are not definitely known, probably enters the lumen of a uriniferous tubule in a fluid or plastic state. It there hardens into a mold, which, when washed out by the [p. 114] urine, retains the shape of the tubule, and contains within its substance whatever structures and débris were lying free within the tubule or were loosely attached to its wall. If the tubule be small and have its usual lining of epithelium, the cast will be narrow; if it be large or entirely denuded of epithelium, the cast will be broad. ”

“ The greater portion of the kidneys, at least their anterior half, has all the appearance of a degenerating organ and is on the way to losing its urinary function, although it still possesses Malpighian bodies and complete ducts ”

“ The Dipnoi or mudfish are remarkable for having a cloacal caecum which probably functions as an urinary bladder. It is situated on the dorsal wall of the cloaca and is not homologous with the allantoic bladder of higher forms. A good deal of the kidney (mesonephros) as it appears to the naked eye is composed of lymphoid tissue.
In the Amphibia the snake-like forms (Gymnophiona) show a very primitive arrangement of the kidney tubules, each having its nephrostome, Malpighian capsule and short convoluted part leading to the Wolffian duct which acts both as ureter and vas deferens. ”

“ Wheeler thus sums up our present knowledge regarding the number and homologies of the Malpighian or urinary tubes:
1. It is very probable that the so-called Malpighian vessels of Crustacea and Arachnida are not the homologues of the vasa Malpighi of the Eutracheata (insects and myriopods) .
2. The Malpighian vessels of the Eutracheata arise as paired diverticula of the hind-gut and are, therefore, ectodermal.
3. In no insect embryo are more than six vessels known to occur; although frequently only four are developed. ”

“ After separating the true cases of chronic parenchymatous nephritis—cases in which only the epithelium of the tubes and of the Malpighian capsules is changed—all the other kidneys of chronic Bright's disease present essentially the same lesions and give rise to the same symptoms.
We can indeed often tell during the life of the patient whether he has large white or atrophied or waxy kidneys, but in many cases such a diagnosis is impossible. ”

“ They are mostly enlarged, congested, and flabby, with extravasations under the capsule, and show microscopic changes essentially consisting in a fatty degeneration of the epithelium. In cases attended with hæmorrhage, the tubuli may be here and there filled with blood. The fatty epithelium is especially seen in the contorted tubes, and the walls of the vessels, both of the capsule and of the malpighian bodies, also undergo the same fatty change. In cases in which death has occurred rapidly, the kidneys have been found almost healthy, or a little congested only. ”

“ Outside the medullary substance and just under the capsule is the cortex, containing the Malpighian bodies, blood-vessels, and the convoluted tubules or loops of Henle. Each Malpighian body contains within a capsule a plexus of capillaries, the glomerulus, with an afferent arteriole and an efferent vein. The renal artery is a branch of the aorta and the nerves are from the solar plexus. ”

“ In Protopterus the vasa efferentia are reduced to a single one on each side at the extreme hind end of the testis.
Teleostomi.—In the actinopterygian Ganoids a well-developed testicular network is present; e.g. in Lepidosteus25 numerous vasa efferentia arise from the testis along nearly its whole length and pass to a longitudinal canal lying on the surface of the kidney, from which in turn transverse canals lead to the Malpighian bodies. (In the case of Amia they open into the tubules or even directly into the mesonephric duct.) ”

“ From the fore-end of the hind-gut arise the slender Malpighian tubes (fig. 12, k) , which have a renal function.
On either side of the gullet are from one to ten pairs of salivary glands (fig. 12, s) whose ducts open into the mouth. Some of these glands may be modified for special purposes—as silk-producing glands in caterpillars or as poison-glands in blood-sucking flies and bugs. The food passing into the crop is there acted on by the saliva and also by an acid gastric juice which passes forwards from the stomach through the proventriculus. ”

“ A series of involutions from the body-cavity are developed; these soon form convoluted tubes, which become branched and interlaced with one another, and also unite with the primitive duct of the kidneys. Owing to the branching and interlacing of the primitive segmental tubes, the kidney is not divided into distinct segments in the same way as with the Selachians. The mode of development of these segmental tubes was discovered by Götte. Their openings are ciliated, and, as Spengel (loc. cit.) and Meyer (loc. cit.) have independently discovered, persist in most adult Amphibians. ”

“ Tubes of renal excretory function in a like position occur in most terrestrial Arthropoda—viz. in Chilopoda, Diplopoda and Arachnida. They are also found in some of the semi-terrestrial and purely aquatic Amphipod Crustaceans. But the conclusion that all such tubes are identical in essential character seems to be without foundation. The Malpighian tubes of Hexapods are outgrowths of the proctodaeum, but those of Scorpion and the Amphipod Crustacea are part of the metenteron or endodermal gut, though originating near its junction with the proctodaeum. ”

“ In the spleen the pulp at first increases and the Malpighian bodies enlarge, but ultimately there is such a development of the fibrous reticulum that the consistence is greatly augmented and the organ becomes indurated. Histologically, there is very little distinction to be made between forms of chronic enlargement of this organ. In the lymph-glands there is increase in the cells; the tissue becomes more succulent, and is in a state of hyperplasia which may terminate in a great development of the fibrous elements, with induration. ”

“ There are diverticula connected with the true stomach. The Malpighian tubes are elongate {284}and extremely numerous. The pair of testes is united in a single envelope. The form and arrangement of the ovaries is remarkable (Fig. 169) ; the egg-tubes are united by the convergence of their terminal threads into a single mass; outside of each ovary there extends a large calyx, into which the tubes open; each calyx is prolonged at its extremity, and forms a long, convoluted tube. ”

“ The influence of many well-recognized pathological states in bringing about venous stasis, and that delay of the blood in the renal—and more especially the Malpighian—vessels which seems the most essential factor in the secretion of albumen, is well known, and its recognition is of much importance in diagnosis and prognosis, since the unfavorable signification of albuminuria in certain cases is liable to be overrated, and a diagnosis of chronic renal disease made to depend upon symptoms which really belong to some other affection. ”

“ The kidneys extend along the whole length of the body-cavity; and the ureter, which does not reach the whole length of the kidneys, is a thin-walled wide duct lying on the outer side. On laying it open the numerous apertures of the tubules for the kidney are exposed. The Müllerian duct, which opens in both sexes into the abdominal cavity, ends, according to Leydig, in the cases of some males, blindly behind without opening into the ureter, and Müller makes the same statement for both sexes. ”

“ Biting mandibles; second maxillae incompletely or completely fused; often forming a suctorial proboscis. Prothorax small, and united to mesothorax. First abdominal segment united to metathorax. Wings membranous, fore-wings larger than hind-wings. Ovipositor always well developed, and often modified into a sting. Numerous (20-150) Malpighian tubes (in rare cases, 6-12 only) . Larva eruciform, with seven or eight pairs of abdominal prolegs, or entirely legless. Pupa free.
Includes two sub-orders:—
1. Symphyta: Abdomen not basally constricted. ”

“ Medial to the Wolffian duct is a tubule (wt) , which seems to be the same as those which were called Wolffian tubules in the preceding stage, but which may be the beginning of the ureter.
Figure 13f, about two hundred and fifty sections posterior to the last, passes through the extreme posterior end of the embryo. The section is nearly circular in outline and is somewhat larger than the preceding. The amnion (a) completely encircles the embryo. The ectoderm (ec) is of fairly even thickness, and the mesoblast which it encloses is of the usual character. ”