Lateral Ducts Research Articles

0-D Dynamic Performance Simulation of Hydrogen-Fueled Turboshaft Engine

In the last few decades, the problem of pollution resulting from human activities has pushed research toward zero or net-zero carbon solutions for transportation. The main objective of this paper is to perform a preliminary performance assessment of the use of hydrogen in conventional turbine engines for aeronautical applications. A 0-D dynamic model of the Allison 250 C-18 turboshaft engine was designed and validated using conventional aviation fuel (kerosene Jet A-1). A dedicated, experimental campaign covering the whole engine operating range was conducted to obtain the thermodynamic data for the main engine components: the compressor, lateral ducts, combustion chamber, high- and low-pressure turbines, and exhaust nozzle. A theoretical chemical combustion model based on the NASA-CEA database was used to account for the energy conversion process in the combustor and to obtain quantitative feedback from the model in terms of fuel consumption. Once the engine and the turbomachinery of the engine were characterized, the work focused on designing a 0-D dynamic engine model based on the engine’s characteristics and the experimental data using the MATLAB/Simulink environment, which is capable of replicating the real engine behavior. Then, the 0-D dynamic model was validated by the acquired data and used to predict the engine’s performance with a different throttle profile (close to realistic request profiles during flight). Finally, the 0-D dynamic engine model was used to predict the performance of the engine using hydrogen as the input of the theoretical combustion model. The outputs of simulations running conventional kerosene Jet A-1 and hydrogen using different throttle profiles were compared, showing up to a 64% reduction in fuel mass flow rate and a 3% increase in thermal efficiency using hydrogen in flight-like conditions. The results confirm the potential of hydrogen as a suitable alternative fuel for small turbine engines and aircraft.

The underestimated posterior lymphatic drainage of the prostate: An historical overview and preliminary anatomical study on cadaver.

The evidence of pelvic lymph node metastases after radical prostatectomy (RP) with pelvic lymph node dissection (PLND) is one of the strongest prognostic factors for poor oncologic outcome. The extent of PLND, although representing a crucial step in RP, is still controversial. Currently, there is a critical drawback in clinical practice due to the lack of congruence between the known lymphatic drainage and cancer dissemination despite defined management by a surgical approach. We hypothesized the existence of alternative pathways for the lymphatic drainage of the prostate currently not considered in clinical daily practice. We carried out a literature review of the anatomic description of nodal drainage of prostate reported by online databases (MEDLINE/PubMed, EBSCO, Web of Science, Ovid, and Scopus) and the original texts since the 18th century, with an additional anatomical dissection on a human cadaver to confirm theoretical data. The anatomical dissection study converged with the historical anatomical treatises in describing three groups of lymphatics devoted to carrying out prostatic nodal drainage. Apart from the ascending ducts from the cranial gland leading to the external iliac nodes; the lateral ducts leading to the hypogastric nodes; small lymphatic vessels from the posterior surface of the prostate, directed to the pararectal lymphatic plexus, in the direction of the lateral sacral lymph nodes and those at the sacral promontory (ie, pararectal and presacral lymph nodes) were observed. Our preliminary findings demonstrate that lymphatic drainage of the prostate extends beyond standard nodal templates actually considered in surgical daily practice, despite the knowledge reported by historical anatomical treatises. Further anatomical and experimental evidence are needed to investigate anatomical variability in humans, as well as to add more topographical details.

Morphostructural investigation on spermatozoa and sperm bundles of the leafhopper Balclutha brevis Lindberg 1954 (Hemiptera: Deltocephalinae)

Morphostructural investigations on male gametes and sperm bundles of Balclutha brevis Lindberg 1954, allochthonous species in Sicily and in mainland Europe, were carried out by light and electron microscopy, since few and fragmented data are known in this respect on leafhoppers, particularly of the subfamily Deltocephalinae. The peculiar feature of the structural organization of B. brevis spermatozoa, for the first time shown in detail within Deltocephalinae, is the presence of apical blebs at the anterior tip of the gametes; moreover, a branching of the flagellar end piece is observed. The sperm bundles of B. brevis, whose genesis occurs in the follicular cysts, also have a peculiar organization within the Cicadomorpha. In fact, the gametes of the bundles are held together by means of membrane junctions between their apical blebs. Sperm bundles remain unchanged up to the lateral ejaculatory ducts where they undergo a rapid disorganization and the gametes, mostly free, are transferred into the female bursa copulatrix and then into the common oviduct, awaiting fertilization. Some spermatozoa isolated from the bundles are found in the seminal vesicles where a spermiophagic activity by epithelial cells is hypothesized.

Description of two new cercariae (an echinostome cercaria and a xiphidiocercaria) procured from Biomphalaria pfeifferi (Krauss) from Nigeria.

During parasitological examination of Biomphalaria pfeifferi snails obtained from Niger state (Nigeria), 2 new types of cercariae were found. They are identified to the level of referring to the major group and described here for the first time. They were examined viable and stained with vital stains as well as fixed in 70% alcohol. They were drawn with a camera lucida and photographed. They are identified as an echinostome cercaria and a xiphidiocercaria. The echinostome is characterized by having a ventral sucker almost double in size the oral one. It has a semicircular structure located beyond the oral sucker. Three pairs of penetration glands are found at the anterior portion of the body. The number of collar spines is relatively large (44-46). The flame cellsare 17 x 2 in number. Two main lateral excretory ducts extend anteriorly, form two typical echinostome loops then pass posteriorly to open together in a diverticulated excretory vesicle. Its tail is relatively long and flattened with 3 fin folds. The tail (640 μm) is longer than the body (475 μm). The xiphidiocercaria belongs to the "ornatae" group. It is relatively small (180.5 x 110 μm) with a long stylet (30 μm). Its oral sucker is one and half times the size of the ventral sucker. Two excretory ducts extend posteriorly in both sides and become dilated and unite to open in a circular excretoryvesicle. Tail is slender shorter than the body and has a dorso-ventral fin fold.

Degree of bile-duct dilatation in liver-transplanted patients with biliary stricture: a magnetic resonance cholangiography-based study

This study assessed whether the degree of bile-duct dilatation in liver-transplanted patients is correlated with the time from intervention and the type of underlying biliary stricture. Fifty-seven 3D magnetic resonance cholangiograms (MRCs) performed on 42 liver-transplanted patients were retrospectively evaluated. Diameter was measured at the level of the extrahepatic bile duct (EBD), right hepatic duct (RHD), left hepatic duct (LHD), anterior and posterior right hepatic ducts (aRHD, pRHD) and left lateral and medial ducts (LLD, LMD). Data were stratified according to the type of biliary stricture (all types, anastomotic, ischaemic-like, mixed) and compared, on a per-examination basis: (a) between two groups based on time from transplantation using a 1-year threshold (nonlongitudinal analysis); (b) among 26 repeated examinations on 11 patients (longitudinal analysis); (c) among different stricture groups. The biliary tree was slightly dilated within 1 year from transplantation (2.9±1.3 to 6.1±3.2 mm). In general, nonlongitudinal analysis showed minimally larger duct size after 1 year (mean +1.4±0.5 mm) despite significant differences at most sites of measurement considering all types of strictures (p<0.01; Mann-Whitney U test). Longitudinal analysis showed diameter increase over time, although without statistically significant differences (p>0.01; Kruskal-Wallis test). No significant difference in bile-duct size was observed when comparing types of stricture (p>0.01; Kruskal-Wallis test). Biliary dilatation after liver transplantation is mild and develops slowly regardless of the underlying type of stricture, possibly in relation to graft properties. MRC has a potential role as first-line imaging modality for a reliable assessment of biliary dilatation and the presence of a stricture.

Pediatric Frontal Mucocele Secondary to a Bifid Frontal Sinus Septum

A mucocele is a mucus-containing sac lined with epithelium that arises within a sinus when its drainage is compromised. The frontal sinus is the most common location, with frontal mucocele development occurring when the nasofrontal duct becomes obstructed because of polyps, bone tumors, prior surgery, sinusitis, trauma, or anatomic variation. We report an unusual case of a sterile pediatric frontal mucocele presenting as a slowly enlarging forehead mass due to a bifid frontal sinus septum. A 9-year-old girl presented to the craniofacial clinic for evaluation of a right frontal mass that had been slowly growing over the past year. She was otherwise healthy and had no history of previous trauma or sinus infections. Computed tomography (CT) scan results revealed a localized frontal fluid collection with protrusion and thinning of the anterior frontal bone between 2 midline bony septii. Surgical cranialization of the frontal sinus was performed. The anatomy of her lesion seen both on CT scan and intraoperatively likely explains this unusual case presentation. Instead of the usual inciting event of an intact frontal sinus drainage system becoming blocked, this patient seemed to have a primary developmental lack of any drainage system that led to her mucocele. During formation of her frontal sinus, she developed a bifid septum within the midline that excluded a portion of her frontal sinus from the lateral nasofrontal ducts. With mucus-producing epithelium trapped within these bony confines, pressure began to mount with expansion and thinning of the bone both anteriorly and posteriorly. The lack of any infectious symptoms and sterile culture results may support that this space developed primarily and was never in continuity with the external drainage system. Only 4 other patients have been reported with asymptomatic forehead swelling as the only presenting symptom, with the age ranging from 33 to 79 years. This patient represents the first clinical report of a congenital developmental mucocele.

3D Anatomical Variations of Hepatic Vasculature and Bile Duct for Right Lateral Sector of Liver with Special Reference to Transplantation

To achieve a safer living related liver transplantation (LRLT) using the right lateral sector, anatomical variations of the portal vein, hepatic artery and bile duct for the right lateral sector and their three dimentional (3D) relationship were assessed by integrated 3D-CT images. 52 patients who underwent contrast enhanced multi-detector row CT (MD-CT) and MD-CT cholangiography were enrolled. Data from contrast enhanced MD-CT were used to reconstruct the 3D images of the hepatic artery and portal vein. 3D images reconstructed from MD-CT data of the hepatic artery, portal vein and bile duct were integrated into a single image. The dual branching of the right lateral portal vein was observed in 22 (42.3%) patients. Three (5.8%) had dual right lateral ducts and 14 (26.9%) had dual right lateral arteries. Among them, "south-turning" artery and "north-turning" bile duct was observed in 22 (42.3%). "South-turning" artery and "south-turning" bile duct were 3 (5.8%). "North-turning" artery and "north-turning" bile duct were 2 (7.4%). Only 27 (51.9%) had single portal vein, bile duct and artery for the right lateral sector, those were preferable as candidates for right lateral sector graft transplantation. 3D anatomical variations of portal vein, artery and bile duct for the right lateral sector were complexed, and only half of the donor candidates had preferable hepatic structures for right lateral sector graft transplantation. Understanding of the 3D hepatic structures by 3D-CT may contribute to a better definition of anatomical contraindications for LRLT which may further results in more safe and widely applied right lateral sector graft LRLT.

Perihilar cholangiocarcinoma arising in hepatitis C virus-related liver cirrhosis with hepatocellular carcinoma

Liver cirrhosis is reportedly one of the conditions preceding peripheral-type intrahepatic cholangiocarcinoma but not hilar/perihilar cholangiocarcinoma. Herein, we report a case of perihilar cholangiocarcinoma arising in a hepatitis C virus-related cirrhotic liver. The patient was a 69-year-old man. He was diagnosed with hepatitis C virus-related chronic hepatitis at the age of 56 years, and 9 years later, multiple hepatocellular carcinomas were detected by imaging modalities. Despite treatments, including chemotherapy, he died of hepatic failure at the age of 69 years. At autopsy, in addition to multiple nodules of hepatocellular carcinoma, we found a white mucinous and fibrous tumor spreading from the hepatic hilum to the periphery along the left lateral segmental bile ducts in the advanced cirrhotic liver. This tumor was histologically a cholangiocarcinoma that involved mainly the peribiliary glands and showed variable cystic dilation, suggesting that it might have been derived from these peribiliary glands. Immunohistochemically, the cholangiocarcinoma cells were positive for cytokeratin 7 and mucin core protein 1, and negative for cytokeratin 20 and mucin core protein 2. Hilar/perihilar cholangiocarcinoma arising in hepatitis C virus-related liver cirrhosis has rarely been reported. This case warrants further studies to clarify the possible involvement of hepatitis C virus in tumorigenesis of hilar/perihilar cholangiocarcinoma.

An ultrastructural study of excretory system development in the cercariae of Prosorhynchoides gracilescens (Rudolphi, 1819) and Prosorhynchus squamatus Odhner, 1905 (Digenea, Bucephalidae).

The ultrastructure of the developing excretory system of Prosorhynchoides gracilescens and Prosorhynchus squamatus cercariae is described. The development pattern was similar in both species. In early embryos the two main collecting tubes were composed of a layer of cells which were wrapped around the lumen. Later, the tubes fused and the excretory epithelium of the fusion zone and that of the lateral caudal ducts became a syncytium. The collecting tubes in the cercarial body retained their cellular organization. As the tails grew, additional excretory pores were formed in the tail stem where thickened portions of the caudal duct epithelium contacted the surface tegument. Following this, the distal portions of the lateral caudal ducts lost contact with the primary excretory pores and progressively degenerated. Excretory atrium development started with differentiation of secretory active cytons peripheral to the fusion zone. These cells gave rise to cytoplasmic extensions that penetrated the fusion zone wall to eventually form a continuous cytoplasmic layer. This layer eventually replaced some of the fusion zone excretory epithelium and became the lining of the excretory atrium. The anterior end of the fusion zone differentiated into an excretory bladder and a short posterior portion gave rise to the caudal vesicle.

An ultrastructural study of the cercarial excretory system in Bucephaloides gracilescens and Prosorhynchus squamatus.

The ultrastructure of the flame cells, capillaries, collecting tubes, excretory bladder, excretory atrium, caudal vesicle, lateral caudal ducts and excretory pores of cercariae of Bucephaloides gracilescens (Rudolphi, 1819) Hopkins, 1954 and Prosorhynchus squamatus Odhner, 1905 (Digenea: Bucephalidae) is described. Both species are essentially similar except for some details. The terminal parts of the protonephridia have all the structural features that are typical of trematodes. The collecting tubes in the cercarial body are composed of cells that are wrapped around the lumen. The main collecting tubes are joined to the excretory bladder syncytium by septate junctions. Features of P. squamatus excretory bladder epithelium indicate that it is involved in secretory activity, but this is not the case in B. gracilescens. In both species the luminal surface of the excretory bladder epithelium is increased by lamellae, and the basal plasma membrane forms invaginations. In the bladder syncytium of P. squamatus both apical lamellae and basal invaginations are more developed and mitochondria are also more numerous. The excretory atrium is lined by a syncytium with nucleated cytons located in the surrounding parenchyma. The atrium lining is not continuous with the body tegument and possesses specific secretory inclusions and a thick glycocalyx. Septate junctions connect the atrium syncytium to the excretory bladder epithelium at its anterior end and to the syncytial excretory epithelium lining the caudal vesicle and the lateral caudal ducts at its posterior. In the excretory pores the caudal duct syncytium is joined to the tegument by septate desmosomes.

Ultramorphology and histology of the larval salivary gland of Pachycondyla villosa (Fabricius) (Hymenoptera: Formicidae, Ponerinae)

The salivary gland possesses a single anterior duct with a columnar epithelium, two lateral ducts with simple cubical epithelium, which becomes columnar in the proximal portion, and two thin-walled reservoirs, from which two secretory regions arise. The dorsal and ventral branches of the secretory regions are connected via transverse commissures and ends in a loop. The secretory region is uniform and consists on a simple cubical epithelium. This paper also presents a review on the morphology of the salivary glands in insects, mainly in Hymenoptera-Aculeata.

Morphology of the sweet potato whitefly,Bemisia tabaci (Homoptera, Aleyrodidae) relative to virus transmission

The stylet bundle of the sweet potato whitefly,Bemesia tabaci, consists of paired mandibles and maxillae. The latter interlock to form the food and salivary canals. Its salivary system consists of paired primary and accessary glands in the thorax. Primary and accessory gland ducts on each side of the nerve cord fuse to form lateral ducts that course anteroventrally to the midline and continue in parallel down the hypopharynx to eventually fuse to form the single afferent duct of the salivary pump. Saliva exiting the pump via the efferent duct enters the salivary canal of the maxillae. Food from the maxillary food canal passes from the antecibarium to the postcibarium or sucking pump and, per os, to the pharynx and esophagus of the foregut. The esophagus extends from the head to the base of the abdomen where it and the anterior midgut intimately mingle with the anterior hindgut to form a filter chamber. The midgut then proceeds dorsocaudally before looping anteroventrally to join the hindgut. The latter gives off two fingerlike Malpighian tubules before entering the filter chamber, whence it proceeds dorsocaudally to the anus within the vasiform orifice. Where possible, the morphology ofBemisia is discussed in relation to plant virus transmission and the morphologies of more thoroughly studied homopteran vectors such as aphids and leafhoppers.

Autologous regulation of androgen receptor messenger ribonucleic acid in the separate lobes of the rat prostate gland.

Differential autoregulation of androgen receptors (AR) has been previously described for the separate lobes of the rat prostate gland. While AR are up-regulated by testosterone in the ventral, dorsal, and LP1 lateral lobes, the epithelial cells of the LP2 lateral ducts show continued expression of the AR protein following androgen withdrawal. To determine the mechanism of this differential autologous regulation, the present study examined the autoregulation of AR mRNA in the separate regions of the rat prostate gland. Northern blot analysis revealed that AR mRNA levels are down-regulated by androgens in all prostate lobes, since their levels increase following castration and decrease upon testosterone replacement. In situ hybridization confirmed that the increase in AR mRNA levels immediately following androgen withdrawal is due to increased transcripts per cell. When normalized to DNA content, the AR mRNA elevation upon androgen withdrawal was transient, and the value returned to control levels in the ventral and dorsal lobes within three days, while the elevation of AR message in the lateral lobe was prolonged. Quantitative reverse transcriptase-polymerase chain reaction studies revealed that elevated AR mRNA levels in the prolonged absence of androgens were confined to the LP2 ducts of the lateral lobe. Nuclear run-on experiments showed no alteration in AR gene transcription two days after castration in the ventral, dorsal, or LP1 lateral lobes when compared to the values in intact rats, indicating that posttranscriptional mechanisms are involved in AR mRNA autoregulation. In contrast, the AR gene transcription rate doubled in the lateral LP2 ducts. The elevated AR mRNA levels in the LP2 ducts due to increased AR gene transcription following castration may, in part, explain the continued expression of AR protein in that region in the absence of testosterone. However, the mechanism whereby AR translation becomes uncoupled from its AR mRNA levels in the ventral and dorsal lobes after hormone withdrawal remains unclear. In summary, the present data demonstrate that differences exist in AR mRNA regulation within the different regions of the rat prostate gland. These differences may begin to explain differential autoregulation of the AR protein in the separate prostate lobes.

USE OF POWER BALANCE TO MODEL PRESSURES IN BILATERAL JUNCTIONS FOR CONVERGING FLOW VENTILATION SYSTEMS

Little information is available on the nature of converging flow in bilateral junctions. Industrial Ventilation (American Conference of Governmental Industrial Hygienists) recommends against bilateral junctions without providing any justification. The American Society of Heating, Refrigerating and Air-Conditioning Engineers provides a table of coefficients for one type of bilateral junction, but it is of limited use in converging flow ventilation systems. The authors experimentally determined losses in one symmetrical bilateral junction designed to connect two 12.7 cm lateral ducts (both 45° entries) and one 17.8 cm collinear duct to a 25.4 cm main duct. Velocity ratios of the converging ducts were varied from 0–3.7 to produce 35 test conditions. The linear kinetic power model provided a good fit to the empirical data. As expected, power losses were lowest when velocity ratios were near unity. Compared for practical conditions to two single lateral junctions in an optimum layout, the power losses in the bilateral junction tested were 0–51% higher—a maximum increase equivalent to about 1.25 relatively smooth elbows. Those costs may be acceptable when weighed against the convenience of bilateral junctions in system layouts. Furthermore, under conditions where bilateral junctions would be convenient to use, actual losses for single-lateral junctions may be higher than those for bilateral junctions.

Use of Power Balance to Model Pressures in Bilateral Junctions for Converging Flow Ventilation Systems

Little information is available on the nature of converging flow in bilateral junctions. Industrial Ventilation (American Conference of Governmental Industrial Hygienists) recommends against bilateral junctions without providing any justification. The American Society of Heating, Refrigerating and Air-Conditioning Engineers provides a table of coefficients for one type of bilateral junction, but it is of limited use in converging flow ventilation systems. The authors experimentally determined losses in one symmetrical bilateral junction designed to connect two 12.7 cm lateral ducts (both 45° entries) and one 17.8 cm collinear duct to a 25.4 cm main duct. Velocity ratios of the converging ducts were varied from 0–3.7 to produce 35 test conditions. The linear kinetic power model provided a good fit to the empirical data. As expected, power losses were lowest when velocity ratios were near unity. Compared for practical conditions to two single lateral junctions in an optimum layout, the power losses in the bilateral junction tested were 0–51% higher—a maximum increase equivalent to about 1.25 relatively smooth elbows. Those costs may be acceptable when weighed against the convenience of bilateral junctions in system layouts. Furthermore, under conditions where bilateral junctions would be convenient to use, actual losses for single-lateral junctions may be higher than those for bilateral junctions.

Ultrastructure and functional morphology of male genital organs and spermatophore formation inProtodrilus (Polychaeta, Annelida)

The structure and functional morphology of lateral organs and sperm ducts, as well as the mechanisms of spermatophore formation and transfer, are investigated by means of light and electron microscopy in the genusProtodrilus. The sperm ducts are simple, ciliated, intercellular gonoducts with a funnel section surrounded by a thin muscle layer and a tube section opening externally in the anterior region of the lateral organs. No glands are present in the sperm ducts. The lateral organs are formed by long epidermal invaginations enclosing an elongate lumen into which numerous cilia project and a large number of glands open. Five to ten different gland types with strikingly distinctive secretory granules are found in the different species. In addition, special supporting cells, the so-called “sponge cells”, sensory cells and an underlying nervous tissue are developed in the lateral organs. It is stated that apart from some similarities to the ventral atrium ofNerilla antennata no corresponding organs are known within the Annelida. It is argued that inProtodrilus the spermatophores are formed by the lateral organs as there are a high number of glands opening into the lumen of the organ. The possible origin and genesis of the male gonoducts as well as the mode of spermatophore transfer inProtodrilus is discussed.

Phasic activity in the digestive diverticula of the lamellibranch Cyclina sinensis.

The canal system and digestive processes of the digesive gland of Cyclina sinensis were studied in a low intertidal population. Specimens were collected from a low-tide level at the estuary of the Tsuri-River, Fukuoka Prefecture, in February, August and November 1981. The sections were examined after staining with haematoxyline and eosin, Azan or Halmi's trichrome. The gland consisted of branched canal system, which contained four kinsd of canals, main and lateral ducts, secondary duct and blind-ending tubule. The main ducts communicating with the somach were two on each side in this species. The tubule consisted of two kinds of the cells, digestive cell and darkly-staining basophyl cell. The darkly-staining cells were always present at three crypts in cross section of the tubule, and these three groups of darkly-staining cells extended continuously through the length of each tubule to meet at the apex. The cell was smaller and appeared triangular in section, bore a long beating flagellum. The digestive cell was larger, granulated and lacked cilia or flagellum. The cell varied in shape from flattened to cuboidal or columnar in accordance with the state of intracellular digestion. Differences in the morphological appearance of digestive gland tubules were attributed to the changes within the digestive cells, which make up the tubules. These morphological variations could be recognized as five distinct tubule types (holding, absorption, digestion, breakdown, final stage of breakdowm).

Engagement of the phallosome in blowflies

SYNOPSISThe engagement of male and female parts during copulation is described in detail for Lucilia sericata Meigen. The occurrence on the phallosome of lateral ducts and apertures for accessory gland secretion is reported for a number of species of Calliphorinae.

The excretory system of nematodes: structure and ultrastructure of the excretory system of Panagrellus redivivus, Ditylenchus myceliophagus with some observations on D. dipsaci and Heterodera rostochiensis.

The structure and ultrastructure of the excretory system of Panagrellus redivivus, Ditylenchus myceliophagus, D. dipsaci and the second-stage larvae of the Heterodera rostochiensis are described. Panagrellus has two lateral ducts, a median duct and a gland. The two lateral ducts are joined over the anterior part of the oesophageal bulb to form a loop. Anteriorly this loop continues as a median duct, which opens to the exterior in an excretory pit, part of the system lies free in the pseudocoelom. The lumen of the lateral excretory duct and the greater part of the median duct is surrounded by capitate tubules, which open into the lumen of the excretory duct. Capitate tubules develop by the invagination of the hypodermal membranes and lie embedded in thick cytoplasm surrounded by mitochondria. Ensheathed in cell membranes the excretory duct forms an anastomosis in the loop and at three other places along the length of each lateral excretory duct. At these regions there are nerve endings. The excretory gland opens posteriorly into the loop and is full of Golgi complexes, endoplasmic reticulum and secretory granules.In the system of Ditylenchus and the second-stage larva of Heterodera the right lateral duct is absent while the left lateral excretory duct continues anteriorly past the median excretory duct; a true loop is not formed. The median excretory duct lies embedded almost throughout its length in the excretory gland. Capitate tubules are present along the length of the lateral excretory duct, but, unlike Panagrellus, are not present around the median excretory duct. Anastomosis is not formed in the excretory ducts. In other respects the system of the species studied is similar to that of Panagrellus.The capitate tubules form a system of fine microtubules. Their ultrastructure and, particularly, their association with large numbers of mitochondria, is very reminiscent of structures thought to be concerned with an active transport role, related to ionic and osmoregulation in other phyla.The excretory system is almost certainly hypodermal in origin. Differences between the morphology and relations of the median duct of Enoplus (Narang, 1970), on the one hand, and that of the other forms studied suggest that these ducts may have different origins: the presence of separate nuclei in the lateral duct and gland portions of the system would be consistent with this view. It is considered that the two parts may have originated separately and have become joined during evolution. It is also shown that the excretory system of Ditylenchus cannot be derived either from an H-shaped system or from a primitive gland system.I wish to thank Professor C. Ellenby and Mr L. Smith for their helpful criticism.

Pressure variations in lateral air ducts

The variation of static head along a lateral duct was investigated. A theory was developed to predict the static head in a lateral duct of constant cross-section discharging air uniformly along its length. This theory has been used to suggest a design method for achieving uniform distribution of air from a standard lateral air duct of the wire mesh type.