Adjacent Canals Research Articles

INVESTIGATION ON PHYSICOCHEMICAL AND MICROBIOLOGICAL POLLUTION LOAD OF HUDIARA DRAIN AND ITS SUBSIDIARIES/

Majority of Industrial wastewater, both treated and untreated is being pumped into drains in Lahore; mainly converging to Hudiara drain. The same is already polluted when it enters Pakistan’s boundary by wastewater from India and as it passes through Lahore, it’s pollution levels are magnified by addition of mainly Charrar & Sattukatla Drain. In this study we performed weekly complete analysis of some Physicochemical and microbiological analysis of Hudiara drain on point of entry in Pakistan as well as the same for Charrar & Sattukatla Drains. It was observed that the organic loading of wastewater has increased 2-3 times in the last 10 years with maximum values of 1,406 and 413 mg/L obtained respectively. Major factor is the high concentration of suspended solids which ranged from 280 to 701 mg/L as well as high organic decomposition indicated by sulphides upto 23.85 mg/L. Moreover, the baseline pollution load of Hudiara Drain entering Pakistan as well as the pollution load our Industries and Adjacent canals exert directly and indirectly into Hudiara Drain.

Can the detection of second mesiobuccal canals be enhanced based on the volume of adjacent canals?

ObjectivesThe purpose of this study was to evaluate whether the presence of the second mesiobuccal (MB2) canal is related to volumetric differences on the adjacent canals of maxillary molars. DesignForty-seven maxillary first and second molars with and without the MB2 canal were individually scanned using microcomputed tomography (micro-CT). The volume of each canal was measured by an evaluator with experience in micro-CT analysis. The intraclass correlation coefficient (ICC) was obtained. Multiple logistic regression and odds ratio was calculated. To compare the volume of canals in molars with and without MB2, the Mann-Whitney test was applied (α = 0.05). ResultsThe intra-examiner reproducibility was almost perfect (ICC=0.97). Multiple logistic regression demonstrated that the volume of the mesiobuccal (MB1) canal can possibly act as a predictor of the presence of the MB2 canal. It was also found that the MB1 canal volume is larger in molars without the MB2 canal (p = 0.01). No statistically significant difference was observed in the adjacent canals (p > 0.05). ConclusionsDespite the challenging detection of the presence of MB2 canals, clinicians should be aware that MB1 canals of reduced volume are highly suggestive of their presence.

Optimal water distribution model of canals considering the workload of managers

AbstractThe optimal operation of water distribution systems is an important research area for the modernization of irrigation schemes. In this paper, an improved 0–1 programming model is developed. This model has three objectives: minimum time of water distribution, minimum spacing of tertiary canals in a group, and the minimum difference of water distribution duration among tertiary canals in the group. The study results show that with the conventional model, 0–1 programming model and improved 0–1 programming model, the durations for the three models are 159.09, 140.50 and 141.07 h, respectively. The working distances are 44.8, 185.5 and 60.6 km. Compared with the conventional model, the lower canals of the improved 0–1 model are all large flow rate operations, while the conventional model inevitably has small flow rate operations, and the improved 0–1 model greatly reduces the duration of water distribution. Compared with the 0–1 model, the improved 0–1 model divides the adjacent canals into a group as much as possible, and the canals between groups start and end operations at the same time as much as possible, so the improved 0–1 model shortens the working distance of the staff and makes it easy for canal managers to operate canals.

Spatial distribution of per- and polyfluoroalkyl substances (PFAS) in waters from Central and South Florida.

Per- and polyfluoroalkyl substances (PFAS) are notoriously persistent pollutants that are found ubiquitously present in aquatic environments. They pose a big threat to aquatic life and human health given the bioaccumulation feature and significant adverse health effects associated. In our previous study, PFAS were found in surface waters from Biscayne Bay and tap waters from the East coast of South Florida, at levels that arouse human health and ecological concerns. Considering that Florida supports millions population as well as treasured, sensitive coastal and wetland ecosystems, we have expanded the PFAS monitoring study on the occurrence, composition, spatial distribution, and potential sources encompassing tap waters from counties on the West coast of South Florida and Central Florida, and surface waters from Tampa Bay, Everglades National Park adjacent canals, Key West, including Biscayne Bay area. A total of 30 PFAS were analyzed based on solid-phase extraction (SPE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). PFAS were detected in all tap water (N = 10) and surface water samples (N = 38) with total concentrations up to 169ng L-1. Higher PFAS concentrations (> 60ng L-1) are mostly observed from polluted rivers or coastal estuaries in Biscayne Bay, and sites nearby potential points sources (military airbases, wastewater facilities, airports, etc.). Our findings on current PFAS contamination levels from diverse aquatic environments provide additional information for the development of more stringent screening levels that are protective of human health and the environmental resources of Florida, which is ultimately anticipated as scientific understanding of PFAS israpidly growing.

Микробиологический режим в системе Тахтакорпюнских гидротехнических сооружений

One of the most pressing problems of the 21st century is the provision of the population and various sectors of agriculture with high-quality water that meets international standards, while eliminating the shortage of drinking water, as well as the efficient use of water resources. In order to improve the supply of drinking water to the population and the efficient use of water resources in our country, as well as throughout the world, a number of important things have been done. One of them is the construction of a unique system of Takhtakorpu hydrotechnical structures (THS), which is of great strategic importance. The system of hydraulic structures in Takhtakorpu was built on the basis of the project for the expansion and reconstruction of the Samur-Absheron system. It not only meets the water needs of the adjacent territories, but also contributes to an increase in the reserves of the Jeyranbatan reservoir, which is the main source of water on the Absheron Peninsula. The presented article made it possible to study the microbiological state of the Takhtakorpu reservoir and adjacent canals. Based on the results of our laboratory analysis in 2017–2019, we can say that the water in the Takhtakorpu reservoir and the Takhtakorpu-Ceyranbatan water channel is stable and clean. The number of microorganisms in the water of the Valvalacay-Takhtakorpu canal is slightly higher, which can be explained by the passage of the canal through settlements and the mixing of other rivers in the area.

Assessment of per- and polyfluoroalkyl substances in Biscayne Bay surface waters and tap waters from South Florida

Per- and polyfluoroalkyl substances (PFAS) are persistent anthropogenic pollutants present in many environmental media worldwide due to their extensive uses in many industrial and commercial products combined with their high thermal and chemical stabilities. Its ubiquitous presence in surface and drinking water supply and significant adverse health effects observed in wildlife and humans, associated with its bioaccumulation potential, pose big concerns. In this study, we have developed and validated a semi-automated solid phase extraction (SPE) followed by liquid chromatography–mass spectrometry (LC-MS/MS) for the determination of legacy and emerging short-chain PFAS substitutes in surface and tap water at low parts-per-trillion (ppt) levels in South Florida environments. Surface waters from Biscayne Bay and adjacent canals (n = 15) and tap waters from different counties (Miami-Dade, Broward, and Palm Beach County) (n = 21) were collected between October 2020 (wet season) and February 2021 (dry season). Total PFAS concentrations up to 242 ng L-1 (average of 168 ng L-1) were found in tap water from Grapeland Heights, which is the closest location to the Miami international airport that was sampled. The highest average total PFAS level of 106 ng L-1 was observed in surface water from the Biscayne Canal C-8 for the wet and dry season. In general, average total PFAS was higher in tap water (86.3 ng L-1) than in surface waters (46.3 ng L-1), whereas the most predominant and frequently detected PFAS were PFBA, PFBS, PFPeA, PFHxA, PFHxS, PFOA and PFOS. PFAS levels found could represent a high human health risk, and ecological risk based on PFOS levels above recommended thresholds are also noted. Such knowledge on PFAS occurrence, distribution and sources in South Florida will provide essential information for local and regional regulatory agencies related to water quality, further facilitating the development of guidelines and procedures for PFAS pollution control and reduction in Florida.

Pest survey card on Pomacea spp.

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017-0137) at the request of the European Commission. Its purpose is to assist the Member States in preparing their survey activities for Pomaceaspp. using a statistically sound and risk-based pest survey approach.Pomacea spp. are Union quarantine pestswith a restricted distribution in the EU. The apple snail's habitat consists of shallow, aquatic, freshwater areas containing aquatic macrophytes. The area of potential establishment comprises part of southern Europe including the rice-producing areas and most of the wetlands, and the Balkans up to the latitude of the Danube River.The expected rate of natural long-distance spread is low, but on a local and regional level the natural spread is effective and it can be several kilometres per year.Pomaceaspp. are polyphagous;however,the surveys in the EU should mainly focus on rice paddies and adjacent canals and contiguous suitable natural areas. The surveys should focus on the detection of the eggmassesthroughout the rice crop season.Egg masses are laid on emerging surfaces, whereas the snails are amphibian and spend most of their time underwater.If specimens of Pomacea spp. are found, samples should be taken to the laboratory for confirmation of the snail identity based on morphological characteristics and molecular identification methods.

Resin secretory canals in Protium heptaphyllum (Aubl.) Marchand. (Burseraceae): a tridimensional branched and anastomosed system.

Protium heptaphyllum is a Burseraceae species known by the production of aromatic resin with medicinal, economic, and ecological values. Information on the development, architecture, and lifetime of the secretory system are crucial to understand the resin production and contribute to a more sustainable tapping regime. We investigated the histology and ultrastructure of the secretory canals under a developmental point of view. Stem samples were analyzed under light and transmission electron microscopy by conventional and cytochemical methods. Secretory canals, originated from procambium and cambium, occurred immersed in the primary and secondary phloem. Mature canals have a secretory epithelium and a wide lumen where the exudate is accumulated. A sheath of parenchyma cells with meristematic features surrounds the epithelium. The canals originate by schizogenesis and develop by schyzolysigenesis. Canals active in secretion occurred since the shoot apex and near the cambium. In the dilation zone of the secondary phloem, secretory canals exhibit sclerified epithelial and sheath cells and are inactive in secretion. Secreting epithelial cells have subcellular apparatus consistent with oleoresin, polysaccharides, and enzymes secretion. Pectinase and cellulase were cytochemically detected in developing canals and are involved in cell wall changes associated to canal growth and release of exudate. In P. heptaphyllum, the secretory system has a complex structure resultant from longitudinal growth, lateral ramification, and fusion of the adjacent canals, in addition to intrusive growth of both epithelial and sheath cells. Although some anatomical results are already known, ultrastructural data represent the novelty of this work. Our findings can contribute to the establishment of more efficient and sustainable techniques for resin extraction in this species.

Wetland plants as indicators of heavy metal contamination

In this study metal accumulating abilities of three emergent macrophytes (Phragmites australis, Typha capensis and Spartina maritima) were investigated in the urbanised Swartkops Estuary. Plants and sediment samples were collected at seven sites along the banks of the main channel and in adjacent canals. Sediments and plant organs were analysed, by means of atomic absorption spectrometry, for four elements (Cd, Cu, Pb, and Zn). Metal concentrations in the sediments of adjacent canals were found to be substantially higher than those at sites along the banks of the estuary. These differences were reflected in the plant organs for Pb and Zn, but not for Cu and Cd. All three species exhibited significantly higher concentrations of metals in their roots. These species are therefore suitable for use as indicators of the presence and level of heavy metal contaminants in estuaries.

Study of rat lumbar vertebral endplate via micro computed tomography

To reconstruct the 3-dimensional (3D) models of vertebral endplate and internal canal structure based upon the micro computed tomography (MicroCT) scanning data and clarify the structural characteristics and changes of bone, canals and lumbar vertebral endplates with advancing age in SD rats. Lumbar spines from male SD rats aged 3, 9 and 16 months (n = 15 each) were subjected to MicroCT scan. Mimics software was used to reconstruct the 3D models of lumbar vertebral endplate and internal canal structure. The bone volume fraction (BV/TV) of endplate was measured by CTAn software. The rebuilt 3D models of vertebral endplate showed that lumbar endplate was a thin layer of bone and the canals within vertebral endplate formed a ring-shaped canal network after reconstruction. Communicating branches existed between the adjacent canals. Every ring-shaped canal connected with trunk canals lying in the ventral and dorsal portions of endplate. The BV/TV of endplate in the ventral portion was lower than that in dorsal portion (ventral side: 79.9% ± 7.3%; dorsal side: 90.6% ± 6.2%, P < 0.05) and BV/TV increased with advancing age. The canals within rat lumbar vertebral endplate are not haphazard, but regularly arrayed to form a ring-shaped network of many circular canals, communicating branches and ventral and dorsal trunk canals. This canal network provides channels for blood vessels within endplate. The ratio of older rat canals decreases in endplate.

Evaluation and applicability of water quality and nutrients removal by coastal wetlands receiving treated municipal wastewater and its application

PurposeThe purpose of this paper is to evaluate the water quality of the wetland that received treated municipal wastewater for 40 years and its application for nutrients removal and wetland restoration.Design/methodology/approachTo assess the water quality impact of the study, wetland sampling sites were selected to represent the receiving wetland, wetland background, effluent discharge point, and the adjacent canals. Water samples were taken in different seasons of the year and analyzed for water quality parameters including pH, temperature, dissolved oxygen, salinity, chloride, total organic carbon, ammonia, nitrite, nitrate, TKN and phosphorus. USEPA‐approved standard methods were followed and Quality Assurance/Quality Control procedures were compiled. Analysis of variance and Student Newman‐Keuls Post‐Hoc analysis were performed on the sampling results to evaluate the water quality differences among the sampling sites.FindingsNo water quality degradation was detected in the wetland study after receiving treated municipal wastewater for 40 years. Dissolved oxygen, pH and temperature were not different from the background level. Total organic carbon and nutrients levels reduced significantly in the receiving wetland, indicating effective waste assimilation. Salinity in the immediate receiving area was reduced substantially, which offers potential application to buffer saltwater intrusion and wetland restoration.Practical implicationsThe practice in this study offers potential implications in wastewater nutrients removal, wetland restoration, minimizing saltwater intrusion in coastal wetland.Originality/valueThis study investigated the water quality impact in wetland after receiving municipal effluent for 40 years. Results provide evidence of effective assimilation in wetlands and offer potential applications in coastal wetland restoration.

Developmental and structural features of secretory canals in root and shoot wood of Copaifera langsdorffii Desf. (Leguminosae–Caesalpinioideae)

Copaifera langsdorffii Desf., popularly known as copaiba, is an oleoresin-producing tree has been overexploited in Brazil by the pharmaceutical, cosmetic and varnish industries. Despite the long history of the use of this species, the structural knowledge on the resin-producing sites remains inadequate and is limited to the trunk. The aim of this study was to describe the origin, structure and developmental features of secretory spaces present in shoot and root wood of C. langsdorffii, based on the usual techniques of wood anatomy studies. Both root and shoot wood present secretory canals distributed along the marginal parenchyma bands which delimit growth layers. Secretory canals are constituted by a locally biseriate epithelium and lume that contains terpenes. They are arisen in the cambial zone from fusiform cambial initial cells and, eventually, ray initials. The origin of lumen is schizogenous. The epithelial cells have meristematic potential and are responsible for the locally biseriate epithelium. Mature secretory canals are wider and are separated between themselves only by a row of radial cells. The fusion of these adjacent secretory canals is frequent and results from the radial cell collapse. The finding of an interconnected system of resin canals in C. langsdorffii might be of value in terms of sustainable extraction of the resin and realistically assess its sustainable harvest potential.

Water and nutrient budgets of ponds in integrated agriculture-aquaculture systems in the Mekong Delta, Vietnam

A participatory on-farm study analysed water and nutrient budgets of six low and four high water-exchange ponds of integrated agriculture-aquaculture (IAA) farms in the Mekong delta. Water, nitrogen (N), organic carbon (OC) and phosphorus (P) flows through the ponds were monitored, and data on fish production and nutrient accumulation in sediments were collected during a fish culture cycle. Results showed that, on average, only 5-6% of total N, OC or P inputs introduced into ponds were recovered in the harvested fish. About 29% N, 81% OC and 51% P accumulated in the sediments. The remaining fractions were lost through pond water discharges into adjacent canals. Fish yields and nutrient accumulation rates in the sediments increased with increasing food inputs applied to the pond at the cost of increased nutrient discharges. High water-exchange ponds received two to three times more on-farm nutrients (N, OC and P) while requiring nine times more water and discharging 10-14 times more nutrients than the low water-exchange ponds. Water and nutrient flows between the pond and the other IAA-farm components need to be considered when optimizing productivity and profitability from IAA systems.

Selective use and spatial distribution of native and non‐native fish in wetland habitats

AbstractWetland habitats are crucial for many fish species as spawning, feeding or nursery areas, but the major factors that govern their use by fish are poorly identified. In the present study, we aim to investigate the selective use and the spatial distribution of native and non‐native fish species in different types of wetland habitats (grasslands and reed beds) in a large freshwater marsh (North Western France). The selective use was measured by comparing the community that uses wetland habitats to the total community of the marsh (sampled in the permanent aquatic habitats (canals) during the low water period). The spatial distribution was studied by analyzing the presence probability of fish in wetland habitats as a function of the distance from adjacent canals. All sampled wetland habitats were occupied by fish, and the fish community in wetland habitats was dominated by three native (Abramis brama, Scardinius erythrophthalmus and Anguilla anguilla) and three non‐native (Ameiurus melas, Gambusia holbrooki and Lepomis gibbosus) species. Species richness and total fish abundance differed between canals and wetland habitats as a consequence of a variable propensity to use wetland habitats by native (avoidance and preference) and non‐native (no preference) species. Non‐native species were also more abundant in reed beds than in grassland while no differences were observed for native species. Universally, the presence probability of fish always decreased in wetland habitats as the distance from the canals increased and only a narrow area, close to canals (50–80 m), was well used by fish. However, non‐native fish species used over greater distances in reed beds than in grasslands while no differences were observed for native species. Variable interpretations related to species tolerance, reproductive guilds or diet are proposed to understand the mechanisms that might explain the widespread success of non‐native species in this spatially varying environment. Copyright © 2008 John Wiley &amp; Sons, Ltd.

The role of cartilage canals in endochondral and perichondral bone formation: are there similarities between these two processes?

We investigated the development of cartilage canals to clarify their function in the process of bone formation. Cartilage canals are tubes containing vessels that are found in the hyaline cartilage prior to the formation of a secondary ossification centre (SOC). Their exact role is still controversial and it is unclear whether they contribute to endochondral bone formation when an SOC appears. We examined the cartilage canals of the chicken femur in different developmental stages (E20, D2, 5, 7, 8, 10 and 13). To obtain a detailed picture of the cellular and molecular events within and around the canals the femur was investigated by means of three-dimensional reconstruction, light microscopy, electron microscopy, histochemistry and immunohistochemistry [vascular endothelial growth factor (VEGF), type I and II collagen]. An SOC was visible for the first time on the last embryonic day (E20). Cartilage canals were an extension of the vascularized perichondrium and its mesenchymal stem cell layers into the hyaline cartilage. The canals formed a complex network within the epiphysis and some of them penetrated into the SOC were they ended blind. The growth of the canals into the SOC was promoted by VEGF. As the development progressed the SOC increased in size and adjacent canals were incorporated into it. The canals contained chondroclasts, which opened the lacunae of hypertrophic chondrocytes, and this was followed by invasion of mesenchymal cells into the empty lacunae and formation of an osteoid layer. In older stages this layer mineralized and increased in thickness by addition of further cells. Outside the SOC cartilage canals are surrounded by osteoid, which is formed by the process of perichondral bone formation. We conclude that cartilage canals contribute to both perichondral and endochondral bone formation and that osteoblasts have the same origin in both processes.

Sub-irrigation in wetland agriculture

Much has been written about the chinampas of central Mexico. One of the commonly repeated themes is that these wetland fields were self-irrigated from below in a process known as sub-irrigation. According to this model, water infiltrates the planting platforms from adjacent canals and then rises to the root zone by capillary action. Thus, chinampas are thought to have needed little supplemental irrigation, and produced dependable and high yields. Here I report the results of field and lab studies of soils of 10 chinampas in the region east of Xochimilco, in the Mexican Federal District. These interpretations are combined with discussion of maize rooting tendencies, regional rainfall patterns, and the presence of willow tree roots in chinampa soils. I also consider whether farmers strive to create and maintain optimum field morphologies for subirrigation when faced with both flood and drought risk, and when manual irrigation is aready option. I conclude that while sub-irrigation is possible under certain combinations of field morphology, crop type, and soil properties, it was a relatively minor factor in the overall decision-making process of past chinampa farmers, and should not be a major determinant of future planning for chinampa preservation or reconstruction. Furthermore, sub-irrigation must be modeled carefully in relation to soil properties, croptypes, and seasonality if it is to beconsidered a significant function of wetland fields in any context.

Salt balances of inland shrimp ponds in Thailand: implications for land and water salinization

Brackish water ponds for farming black tiger shrimp (Penaeus monodon) have recently proliferated in inland areas of Thailand's central plain, raising concerns about land and water salinization. The environmental impacts of inland shrimp farming were assessed by analysing the salt balance for an inland shrimp farm. Field data on water fluxes and pond salinity, collected from nine ponds in Chachoengsao Province from May–July 1999, were used to model the salt balance for a typical shrimp pond over one growout cycle. During growout, seepage represented 38% (11.5 tonnes crop−1) of salt losses, pond discharge 33% (9.7 tonnes crop−1), and accumulation of salt in pond sediment 6% (1.8 tonnes crop−1). About 23% of the initial salt content remained at harvest and could have been recycled. However, the majority (84% on average) was discharged to the irrigation canals. Much of the salt in pond sediment was also exported to the canal system through tidal flushing of the ponds. Field measurements of salinity were taken in adjacent canals and rice paddies to explore the impacts of salt exports from shrimp ponds. Pond discharge caused increases in canal salinity above levels that would impact on yields of irrigated rice and orchard crops, the main land uses in the region. Elevated soil and water salinity in adjacent rice fields was probably related to lateral seepage from the ponds. The salt budget was also modelled for a zero discharge farming system, promoted by proponents of inland shrimp farming as having few impacts. However, the results suggest that, even in zero discharge ponds, almost half of the initial pond salt content is exported through seepage (45%, 12.4 tonnes crop−1), with another 6% (1.8 tonnes crop−1) deposited in sediments. While techniques exist for mitigating much of the salt leakage, the likelihood of their uptake in Thailand is low. Further expansion of inland shrimp farming in the central plain is therefore likely to contribute substantial salt load to the area's land and water resources.

Intrachondral microvasculature in the human fetal talus.

The intrachondral microvasculature of the growing talus of human was studied in 16 fetuses aged from 15 to 44 weeks of gestation, using interrupted serial sections and vascular injection of ink. The cartilage model of the talus was shown to be well vascularized throughout by cartilage canals. The cartilage canal contained blood vessels and connective tissue, with vessels originating from the perichondrial vessels. They were covered by a thick connective tissue wall that was continuous with the perichondrium. The functions of the cartilage canals were mainly to nourish the large masses of cartilage and to supply osteogenic tissue, which initiates the primary ossification center. As in the adult, the fetal talus was supplied with four to five main branches originating from the sinus tarsi and the tarsal canal; there were no anastomoses between the vessels of the adjacent cartilage canals and between the branches within the cartilage canal. This type of microvasculature is vulnerable to injury and, if impaired, may cause serious complications.

Temporal patterns of emergence of the riverine dragonfly Onychogomphus uncatus (Odonata: Gomphidae)

The emergence of Onychogomphus uncatus from three stretches at two adjacent canals in Southern France was compared in 1993. Whereas 50% of annual emergence from the two stretches at one canal had occurred after 25 and 36 days, respectively, it had occurred after 5 days at the second, where emergence began 14 days earlier. At the second canal most of the larvae of one generation had overwintered in the final instar but at the first canal only half did so. These differences correlate with greater annual fluctuations of temperature at the second canal which are responsible for high temporal synchronisation. Other factors that may cause differences in seasonal regulation, such as drying up and density, are discussed. Differences exist also in sex ratio and abundance of emerging individuals, particularly between the two collection sites at the first canal.

Morphological observations concerning the pattern of mineralization of the normal and the rachitic chick growth cartilage.

The entire calcified layer of the chick growth cartilage is penetrated by canals that contains blood vessel complexes: some of these canals pass through all the layers of the cartilage from the resorptive zone at the metaphysis, through the mineralizing, hypertrophic, proliferative and resting regions. This study aimed to provide more details of the 3-D microanatomy of this region and to establish whether there are differences in the process and progress of mineralization compared with the established mammalian "model". Proximal tibial heads from 6 to 8 weeks old normal and vitamin D deficient chickens were rapidly frozen and prepared for scanning electron microscopy using freeze-fracture, freeze-drying, plasma ashing, and chemical deproteinization techniques. Cartilage samples were also embedded in PMMA and polished for BSE imaging. Other samples were prepared for light microscopy. Zones of (mineralized) cartilage several cells thick separate adjacent canals. At the mineralizing front, calcification of the matrix is most advanced close to the canals, but the matrix adjacent to the canal lumens does not calcify. Mineralisation of the cartilage matrix is incomplete and small fenestrae of unmineralized matrix connect chondrocyte lacunae. These discontinuities in matrix calcification could serve as a route for diffusion of nutrients, metabolites and dissolved gases. The calcified cartilage is more mineralized than the contiguous developing bone. Osteoblasts surrounded by bone were seen to occupy the lacunae of hypertrophic chondrocytes. We tentatively suggest that some osteoblasts represent a terminal stage in the differentiation of hypertrophic chondrocytes. The rachitic cartilage was disorganised. It was penetrated by irrugular vascular canals and exhibited a greatly expanded hypertrophic zone.(ABSTRACT TRUNCATED AT 250 WORDS)