Kinds Of Needles Research Articles

Investigation of an Improved Side-Vented Needle and Corresponding Irrigation Strategy for Root Canal Therapy with CFD Method

Background and Objective: This research aimed to present an improved side-vented needle and explore its availability as well as the corresponding irrigation strategy. Methods: A CFD model was used to simulate the irrigant flow in a simplified prepared round root canal with an apical delta respectively with different needles for irrigation. The needle types include flat end-tip needle, original side-vented needle, and improved side-vented needle. Different insertion depths and inlet velocities were contrastively studied, as well as the gap size between the bulb at the end tip of the improved side-vented needle and the root canal. The study includes a total of 13 schemes. Velocity, pressure, and shear stress in the root canal were measured to contrast the internal flow-field details and irrigation efficiencies between different schemes. Results: Poor irrigation replacement appeared in the schemes without enough needle insertion no matter which kind of needle has been used, though relatively lower pressure emerged at the apical foramen. On the contrary, deepening needle insertion not only brings better irrigant replacement but also higher apical foramen pressure. The original side-vented needle tends to make lower pressure at the apical foramen and simultaneously worse irrigant replacement as compared to the flat end-tip needle. The fluid entering the apical anatomy part deceases a lot as the original side-vented needle was replaced by the improved one. The scheme using the improved side-vented needle with gap size ratio and inlet velocity respectively equaling 5.0% and 5.50m/s can be considered the best one. Conclusions: The improved side-vented needle can ensure acceptable irrigant replacement performance without leading to a high-pressure level at the apical foramen. The gap between the bulb and the wall of the root canal is very crucial for the pressure at the apical. The ideal irrigation strategy is ensuring the gap equals zero. However, it is a little hard to realize during the whole procedure of the root canal preparation except the final step. Consequently, another strategy that keeping the value of gap size ratio as small as possible such as less than 15% and simultaneously ensuring lower-velocity coming fluid, is necessary in the non-final irrigation.

Finite element analysis and experimental study of the performance of insulin pen needles

Objective To compare and analyze the relationship between geometric parameters of the needle of different insulin pens and their puncture force, flow rate, and pressing force. Methods The human skin tissue model and needle model were established, and the finite element simulation analysis of needle puncture was performed. Using a test platform, 25 kinds of needles with different geometric parameters were tested for the puncture force, pushing pressure, flow rate and other parameters. The influence of geometric parameters on the performance of the needles were analyzed. Results The puncture force of the needle was closely related to its section design. Compared with the three-section needle, the five-section needle increases the secondary inclination angle and the condyle angle, increases the contact area between the needle and the tissue, and make the change of the contact angle more smoothly, which reduce the needle penetration force. The smaller the outer diameter of the needle, the smaller the penetrating power. The larger the inner diameter of the needle, the greater the fluid flow rate, the smaller the pushing pressure, and the higher the injection accuracy. Conclusions Five-section, ultra-thin-walled or ultra-thin-walled needles have more excellent performance. On the basis of ensuring the strength of the needle, the needle's geometry can be optimized to reduce the puncture force. The results of this study can provide theoretical basis and experimental basis for the design of needles for insulin pens. Key words: Insulin pen needle; Puncture force; Flow rate; Finite element analysis

Needle aspiration versus intercostal tube drainage for pneumothorax in the newborn.

Pneumothorax occurs more frequently in the neonatal period than at any other time of life and is associated with increased mortality and morbidity. It can be treated with either aspiration with a syringe (using a needle or an angiocatheter) or a chest tube inserted in the anterior pleural space and then connected to a Heimlich valve or an underwater seal with continuous suction. To compare the efficacy and safety of needle aspiration (either with immediate removal of the needle or with the needle left in situ) to intercostal tube drainage in the management of neonatal pneumothorax (PTX). We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2018, Issue 5), MEDLINE via PubMed (1966 to 4 June 2018), Embase (1980 to 4 June 2018), and CINAHL (1982 to 4 June 2018). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. Randomised controlled trials, quasi-randomised controlled trials and cluster trials comparing needle aspiration (either with the needle or angiocatheter left in situ or removed immediately after aspiration) to intercostal tube drainage in newborn infants with pneumothorax. For each of the included trials, two authors independently extracted data (e.g. number of participants, birth weight, gestational age, kind of needle and chest tube, choice of intercostal space, pressure and device for drainage) and assessed the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow-up). The primary outcomes considered in this review are mortality during the neonatal period and during hospitalisation.We used the GRADE approach to assess the quality of evidence. Two randomised controlled trials (142 infants) met the inclusion criteria of this review. We found no differences in the rates of mortality when the needle was removed immediately after aspiration (risk ratio (RR) 3.92, 95% confidence interval (CI) 0.88 to 17.58; participants = 70; studies = 1) or left in situ (RR 1.50, 95% CI 0.27 to 8.45; participants = 72; studies = 1) or complications related to the procedure. With immediate removal of the needle following aspiration, 30% of the newborns did not require the placement of an intercostal tube drainage. None of the 36 newborns treated with needle aspiration with the angiocatheter left in situ required the placement of an intercostal tube drainage. Overall, the quality of the evidence supporting this finding is very low. There is insufficient evidence to establish the efficacy and safety of needle aspiration and intercostal tube drainage in the management of neonatal pneumothorax. The two included trials showed no differences in mortality; however the information size is low. Needle aspiration reduces the need for intercostal tube drainage placement. Limited or no evidence is available on other clinically relevant outcomes.

Microneurography: how it started and how it works.

In the first section, this historical review describes endeavors to develop the method for recording normal nerve impulse traffic in humans, designated microneurography. The method was developed at the Department of Clinical Neurophysiology of the Academic Hospital in Uppsala, Sweden. Microneurography involves the impalement of a peripheral nerve with a tungsten needle electrode. Electrode position is adjusted by hand until the activity of interest is discriminated. Nothing similar had previously been tried in animal preparations, and thus the large number of preceding studies that recorded afferent activity in other mammals did not offer pertinent methodological guidance. For 2 years, the two scientists involved in the research impaled their own nerves with electrodes to test various kinds of needles and explore different neural systems, all the while carefully watching for signs of nerve damage. Temporary paresthesiae were common, whereas enduring sequelae never followed. Single-unit impulse trains could be discriminated, even those originating from unmyelinated fibers. An explanation for the discrimination of unitary impulses using a coarse electrode is inferred based on the electrical characteristics of the electrode placed in the flesh and the impulse shapes, as discussed in the second section of this paper. Microneurography and the microstimulation of single afferents, combined with psychophysical methods and behavioral tests, have generated new knowledge particularly regarding four neural systems, namely the proprioceptive system, the cutaneous mechanoreceptive system, the cutaneous nociceptive system, and the sympathetic efferent system to skin structures and muscular blood vessels. Examples of achievements based on microneurography are presented in the final section.

Finding New Kinds of Needles in Haystacks: Experimentation in the Course of Abduction

Finding New Kinds of Needles in Haystacks: Experimentation in the Course of Abduction

圆利针疗法治疗常见疾病的临床应用

圆利针疗法起源于内经，是灵枢九针之一。灵枢提出圆利针应用，因疾病症状不同所选针也不一样。病证有表里寒热虚实，则针有长短大小宽窄之别。所以本人从圆利针疗法的相关历史文献记载入手，阐述该法的现代临床研究进展，认为圆利针疗法在治疗软组织损伤性疾病，其某些重症、顽症、急症、痛证等疾病方面疗效确切，为相关研究提供参考。 Round sharp needle therapy originated from Neijing, is one of nine kinds of needles. Lingshu said the disease symptoms are different, so needle selection is not the same. Disease has exterior and interior, cold and heat, weak and strong, so the needle have long and short, big and small, wide and narrow. Therefore, I start with the historical records of the round sharp needle treatment, development of the modern clinical research of this method, think round sharp needle therapy treatment of soft tissue damaged diseases, the effect of some severe disease and acute pain syndrome, and other diseases is exact, which provides a reference for related research.

Effect of apical preparation on different needle depth penetration

AimShaping should be complemented by antiseptic solution. These are often delivered using a needle and syringe. But apical penetration of the irrigation solution is of only 1mm beyond its tip. The aim of our study was to evaluate the influence of the apical preparation on the penetration depth of some needles. Methodology24 teeth were divided randomly into two groups and prepared in continuous rotation (350rpm) with Revo-S® or ProTaper® to sizes AS 30, 35 and 40 and F1, F2 and F3 respectively. Four types of endodontic needles were used. Three sizes of stainless steel needles: 25, 27 and 30 gauge and one of nickel–titanium needle: 30 Gauge. Each needle was inserted and its length of penetration measured before the root canal preparation and after the finishing files. ResultsMultivariate analysis of variance showed significant differences for the finishers (p<0.0001) and the kind of needle (p<0.0001). The PLSD Fisher's test can highlight the differences between the six types of apical shaping used (independently of the needle type). The same differences were observed between the four types of needle (independently of the apical finish) (p=0.0232).Variance analysis between the four different needles is statistically significant for each apical shaping (p<0.0001×6). Variance analysis among the six types of finish is statistically significant for each type of needle (p<0.0001×4). ConclusionsThis study shows that the apical preparation influences the penetration depth of needles. The 27 gauge needles reach the last millimetre only with the Revo-S® system shaped with AS 40. Finally, the 30 gauge needles reach it for all finishers except the ProTaper® F1.

Needle aspiration versus intercostal tube drainage for pneumothorax in the newborn.

Pneumothorax occurs more frequently in the neonatal period than at any other time of life and is associated with increased mortality and morbidity. It may be treated with either needle aspiration or insertion of a chest tube. The former consists of aspiration of air with a syringe through a needle or an angiocatheter, usually through the second or third intercostal space in the midclavicular line. The chest tube is usually placed in the anterior pleural space passing through the sixth intercostal space into the pleural opening, turned anteriorly and directed to the location of the pneumothorax, and then connected to a Heimlich valve or an underwater seal with continuous suction. To compare the efficacy and safety of needle aspiration and intercostal tube drainage in the management of neonatal pneumothorax. We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 11), MEDLINE via PubMed (1966 to 30 November 2015), EMBASE (1980 to 30 November 2015), and CINAHL (1982 to 30 November 2015). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. Randomised controlled trials, quasi-randomised controlled trials and cluster trials comparing needle aspiration (either with the needle or angiocatheter left in situ or removed immediately after aspiration) to intercostal tube drainage in newborn infants with pneumothorax. For each of the included trial, two authors independently extracted data (e.g. number of participants, birth weight, gestational age, kind of needle and chest tube, choice of intercostal space, pressure and device for drainage) and assessed the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow-up). The primary outcomes considered in this review are mortality during the neonatal period and during hospitalisation. One randomised controlled trial (72 infants) met the inclusion criteria of this review. We found no differences in the rates of mortality (risk ratio (RR) 1.50, 95% confidence interval (CI) 0.27 to 8.45) or complications related to the procedure. After needle aspiration, the angiocatheter was left in situ (mean 27.1 hours) and not removed immediately after the aspiration. The angiocatheter was in place for a shorter duration than the intercostal tube (mean difference (MD) -11.20 hours, 95% CI -15.51 to -6.89). None of the 36 newborns treated with needle aspiration with the angiocatheter left in situ required the placement of an intercostal tube drainage. Overall, the quality of the evidence supporting this finding is low. At present there is insufficient evidence to determine the efficacy and safety of needle aspiration versus intercostal tube drainage in the management of neonatal pneumothorax. Randomised controlled trials comparing the two techniques are warranted.

The influence of annealing process in the fabrication of helical needles for sutures in deep-wound cavities

The standard procedure of a surgical suture can be very difficult to perform in deep-wound cavities because the available space is not enough to perform the complicated movements required for the knot or to handle the needle. To improve this situation a new kind of hollow, helical needle was developed and filed for patent. To ensure the manufacturability of this kind of needle, a prototype and a prototypical tool were designed and tested. As a prototypical basis, commercially available cannulas were selected. Coil winding was used as a forming process to bring the cannula into the helical form. The material properties of the surgical steel and the work hardening that the semi-finished products underwent lead to challenges for the forming process. The limitations of springback and low formability reduce the possible radius of the helix. Therefore, a soft annealing of the cannula was investigated. However, in surgical needles, stiffness is of great importance. Since hardening by quenching is not possible, annealing parameters were chosen to retain the necessary stiffness. Based on the data obtained from tests of annealing parameters, four final geometries of helical needles were designed and first prototypes were manufactured.

Validity of the “Streitberger” Needle in a Chinese Population with Acupuncture: A Randomized, Single-Blinded, and Crossover Pilot Study

We studied the validity of a “Streitberger” needle as a valid approach in a Chinese population with experience of acupuncture. Volunteers were recruited from students of the School of Acupuncture and Moxibustion, Guangzhou University of Chinese Medicine. Sixty students receiving education in acupuncture theory and experience in practical acupuncture were tested in study determining whether needling with the placebo needle felt any different from conventional acupuncture. Outcomes included measures of penetration sensation, VAS ratings, and Deqi sensation questionnaire. As a result, needle penetration, VAS ratings for either needle and Deqi sensation were not significantly different between two kinds of needles. Our findings show that the use of “Streitberger” needle is credible in a Chinese population with acupuncture experience.

The buttonhole method spreads “Like Wildfire”

The first description of the constant site needle insertion was published in the Polish literature in 1977, and two years later in Dialysis & Transplantation. While those publications did not create much interest, they were noted by Belding H. Scribner, the father of chronic hemodialysis (HD), who taught the method to one of his home HD patients, A. Peter Lundin, who also informed George Harper, another home HD patient from Georgia, about the advantages of the method. But the method was not widely used prior to publication of my 1995 paper in Dialysis & Transplantation. In this paper, I suggested that the method was not widely used due to prevalent graft use, “multiple sticker” practice for buttonhole creation, and the lack of blunter needles. When the method was developed in Poland two kinds of needles were used, very sharp and blunter, which were becoming even blunter because they were reused. This seemed to be advantageous for the constant site method, as a blunter needle tended to go through the established path without cutting the insertion tunnel wall. Blunter needles were not available in the U.S. at the time. Both of the home hemodialysis patients noted above inserted the needles by themselves and were skillful enough to insert them through the established paths, even using sharp needles. The history of the publication of this 1995 paper is interesting. Harper was very much interested in new HD machines. He contacted Rodney S. Kenley, president of AKSYS Ltd., which was in the process of developing a home HD machine based on my patents, and told him about the buttonhole method of needle insertion. In 1994, Kenley called me asking whether I was aware about this method apparently suitable for home HD. I told him that I was aware, as I was the first who described it, but that I was not successful in introducing it into our center in Columbia. He prodded me to work on this problem, as it might be important for our home HD program. I decided to intensify my efforts to introduce this method in the United States, so I submitted the paper to D&T, and invited George Harper to our 1st Symposium on Home Hemodialysis in Baltimore, where he presented his experience with the method. I was also able to get cooperation from William J. Schnell, an engineer at Medisystems Research Corporation in Lakemoor, Ill., to manufacture blunter needles. Gradually, the method started to be used at our Columbia center, and in other centers. Videos were produced describing this technique, and every year more information was presented at the conferences. Other companies (Nipro and JMS North America) started to manufacture blunter needles. Blunter needles are suitable for the use in an established track, which is created with sharp needles during 8 to 12 hemodialysis sessions. As a consequence of the publication in D&T, I received multiple queries from patients and nurses regarding details of the technique. Many nurses started to push for the use of the constant site method and got permissions from nephrologists. Several centers in Seattle, Toronto, Louvain (Belgium), Maastricht (Netherlands), Brazil, and New Zealand started to use the buttonhole method, particularly in home HD patients, with positive results, and most home HD patients started to use this method. Stewart Mott, RN, a blood access nurse at our center in Columbia, Mo., Tony Goovaerts, a nurse from Louvain, Belgium, and Emma Vaux, MD, a consultant nephrologist from Reading, England are very active in buttonhole needle insertion research. Recently, Magda van Loon from The Netherlands, successfully defended her PhD thesis on blood access, with a large portion related to the buttonhole method of needle insertion. I also received an e-mail from Rosa Marticorena, a nurse at St. Michael's Hospital, Toronto, Ontario, Canada, that she plans to write a PhD thesis on the buttonhole method. One of the most active researchers of the buttonhole method was Lynda Ball, RN, BSN, CNN, from the Northwest Kidney Center in Seattle, where many daily dialysis patients were being treated. In an e-mail sent to me in August 2007, she remarked that “buttonhole has caught on like wildfire.” And indeed, numerous papers on the method are being published—all stressing lower pain, lower hematoma formation, fewer missed needle insertions, and better fistula preservation.

From the Editors Publishing Laboratory Research inAMJ: A Question of When, Not If

From the Editors Publishing Laboratory Research in<i>AMJ</i>: A Question of When, Not If

Exclusive Diagnostic Contribution of the Histology Specimens Obtained by 19-Gauge Transbronchial Aspiration Needle in Suspected Malignant Intrathoracic Lymphadenopathy

Transbronchial needle aspiration (TBNA) performed with a 19-gauge needle provides both cytologic and histologic specimens. However, the diagnostic yield for malignancy gained by histologic examination is unclear. Moreover, this kind of needle is often reserved only for selected cases, in part due to fear for complications. The primary aim of this study was to investigate the diagnostic contribution for malignancy added by histologic to the cytologic specimen examination. The secondary aim was to evaluate the safety of using a 19-gauge needle routinely in all patients. Consecutive patients presenting with mediastinal and/or hilar lymph node enlargement of > or = 1 cm, in whom suspicion for malignancy was raised, underwent TBNA with a 19-gauge needle. Patients with negative aspirate test results underwent surgical investigation. Among 77 patients who were examined, 66 had malignant intrathoracic lymphadenopathy. TBNA proved malignancy in 58 patients, whereas it missed the diagnosis in 8 patients (sensitivity, 87.9%; negative predictive value, 57.9%). TBNA established the diagnosis in 94% of patients with small cell lung cancer (SCLC), and in 88% of patients with non-SCLC (p = 0.7). Exclusive diagnosis was obtained in 36.4% of patients by histology (compared with 18.2% of patients by cytology [p = 0.06]), representing an increase of 35.3% in the diagnostic yield of TBNA over sole cytology examination. No major complication occurred. Histology specimens obtained exclusively with a 19-gauge TBNA needle enabled diagnosis in about 36% of patients with malignant intrathoracic lymphadenopathy. The routine use of a 19-gauge needle is safe.

Acupuncture: Its Place in the History of Chinese Medicine

Acupuncture, as an important and unique part of traditional Chinese medicine, has played a major role in the health care of the Chinese people, occupying a significant place in the history of traditional Chinese medicine. This can be seen from the following four points: 1. Acupuncture - One of the Earliest Healing Arts in China Many primary sources show that acupuncture, perhaps together with moxibustion, emerged as one of the earliest healing methods in the history of Chinese medicine. It has been arguably a foremost therapeutic method ever since its development. In the history of Western medicine certain legendary figures, in ancient Greece for example, have been cited as originators of the art of medicine. Similarly in ancient China, three legendary characters have been regarded as the founders of Chinese medicine. The earliest is Fu Xi, also called Bao Xi, a legendary tribe leader who was believed to have made many innovations, such as the production of nine kinds of needles. 1 The second is Shen Nong, the Divine Husbandry Man, who was said to have taught the art of husbandry, and discovered the curative virtues of herbs by tasting a hundred different varieties. 2 The third is Huang Di, the Yellow Emperor, who was said to have discussed medicine, including acupuncture, with his ministers and who, like Fu Xi, was credited with having made nine kinds of needles. 3 These legends reflect, to a certain extent, the historical facts of the early origins of Chinese medicine. We may think of the legendary figures as embodiments of ancient Chinese ancestors

Pre-analytical for biological monitoring of manganese.

Manganese is an essential element but it may result in a toxic event if the workers are excessively exposed to this element. Monitoring of biological Mn exposure is therefore important. The careful preparation for Mn analysis is necessary. In order to get a correct protocol for sampling and storage of the biological samples, identification of the possible contamination source is necessary. This study is concerned with the monitoring procedure of manganese especially the sources of contamination sampling, sample transportation and storage. The results of the study shows that some kinds of needles and anticoagulants might be the main sources of contamination of specimen. It is important to avoid these contamination in performing biological monitoring on workers exposed to manganese.

US-guided breast biopsy with an automated cutting needle

The authors report their experience on the use of a biopsy gun for histological sampling in the field of breast lesions. The use of cytological sampling by (FNAB) fine needle aspiration biopsy has been preferred so far, because it has been thoutht to be simpler, less risky and reliable. Nevertheless, the cytological sampling shows a number of drawbacks such as the need for passes to get sufficient cellular material, frequent problems in diagnosing benign lesions and the decisive influence of the operator's skill. By using a biopsy gun for histological sampling these disadvantages are eliminated. In this case, in fact, the validity of the sample is not influenced by the operator's skill; fewer passes are necessary and their validity does not depend on the nature of the lesion. The personal series of cases involves 91 patients subjected to histological sampling for suspected lesions. Two different kinds of needles were used with one an 18 G diameter and a 23-mm extension of the sytlet, as well as a sampling window 17 mm; the other with the same diameter and extension of the stylet, as as a sampling window 8 mm. The first needle was used in all 91 patients, and the second only in 30. The results were not influenced by the employ of the different kinds of needles. A total of 268 samples were made and 110 lesions were discovered, 79 of which were malignant and 31 benign (fibroadenoma, fibrocystic change and epitheliosis). Three carcinomas were not found (3 false-negative) and one specimen was inadequate. The values of sensibility, specificity and diagnostic accuracy of the method were, respectively, 96.2%, 100% and 97.2%, with 3.8% false-negative due to three cases where the lesion was not centred for guidance mistake.

Litho‐diagenetic implications of the calcium oxalate‐carbonate biogeochemical cycle in semiarid Calcretes, Nazareth, Israel

Abstract Microscopic observations of calcrete soil samples in semiarid environments from Israel reveal a particular vesicular microfabric. The calcrete horizon is indurated but highly porous and all the pores are coated with a gray layer (quasi‐coating) of secondary calcium carbonate. Two kinds of needles are found inside the pores: thin and regular needles (calcite), and filaments with very sharp spikes that are of fungal origin. Analysis of the proportions of C, O, and Ca were made with an E.D.S. microprobe connected with a scanning electron microscope to distinguish calcite (CaCO3) from calcium oxalate (CaC2O4) and to differentiate inorganic from organic influences. Under biological control, calcium oxalate coexists with calcium carbonate; both contribute to rock diagenesis. In the pores, biological activity promotes a complex cycling of calcium leading to recementation of the matrix and further lithification. Thus, this kind of calcrete is due to geological evolution as much as to biochemical control.

Spruce photosynthesis: possibility of early damage diagnosis due to exposure to magnesium or potassium deficiency

The effects of exposure to magnesium or potassium deficiency on spruce needle photosynthesis were studied before symptoms of damage were visible, and recovery was followed. Water content, pigment content and O2 evolution rate were chosen as parameters of physiological activity in addition to chlorophyll fluorescence. In the case of exposure to Mg deficiency, the first symptoms detected by all the physiological parameters were observed in older needles. An effect on chlorophyll fluorescence [decrease in fluorescence index (Rfd) and photochemical quenching (qQ), and increase in non-photochemical quenching (qE)] was detected in younger needles at the beginning of the deficiency treatment with little effect on the other physiological parameters [decrease in water content to 96.5%, and in photosynthetic rate expressed over dry weight (PSDW) to 90.7%]. No recovery was observed. After a K-deficiency exposure, both kinds of needles were affected, but a high recovery rate was observed, especially in the current-year needles, where a complete recovery from damage was detected by fluorescence and confirmed later by visual inspection. Finally, these results indicate the possibility of an important early diagnosis of damage in forest decline and suggest that chlorophyll fluorescence can be used, at least in the laboratory, as a qualitative test of plant health.

THE ADVENTURES OF ANTROBUS

“IT'S no use!” declared Cranmer vehemently, crashing into our office like a wounded rhino and banging about in a most irresponsible manner… “That man Lumsden will have to go!” I recognized the mood as being one of utter frustration; the kind of needle a man gets when his best prospect is filched from under his nose at the precise moment of anticipated triumph. I know the feeling well. Cranmer flung down his document case and slumped into a chair. “He'll have to go, Antrobus!” he repeated firmly, with a seriousness suggesting it was a decision which lay within his gift that he had just resolved after great and protrated heart searching.

SEASONAL GROWTH CHARACTERISTICS OF LONG AND SHORT SHOOTS OF TAMARACK

Tamarack (Larix laricina (DuRoi) K. Koch) produces long shoots which bear two kinds of needles. Early needles are present in the bud and elongate rapidly after budbreak. Late needles, few of which are present in the bud, elongate later than early needles. Short shoots bear early needles only, and stem length seldom exceeds 1 mm. Seasonal changes in length and weight of needles and stems of both shoot types were measured. In long shoots, 75% of stem elongation, more than 70% of stem weight increment, and 65–70% of late needle elongation occurred after early needles were full-sized. Stem and late needle elongation ceased simultaneously, after which time needle weight decreased and stem weight increased. Early needles probably drew on food reserves while developing, and then themselves contributed to stem and late needle elongation. Final stem weight increase probably used photosynthate from both late and early needles of the current year.Shading of current and last year's needles showed that shoots in which photosynthesis was interrupted in this way produced shorter, lighter-weight stems than did control shoots.