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Livestock excreta deposition on concrete farmyards has been identified as an important source of ammonia (NH3) emissions from agriculture. The objective of this study was to quantify the effect of urine application rate and four cleaning strategies on NH3 emissions from excreta deposited on a concrete yard. Three experiments were conducted on a concrete yard over a three week period in August 2016. Experiment 1 consisted of 1 kg dung applied with either (i) 0.67 l urine (1:0.67), (ii) 1 l urine (1:1) or (iii) 2 l urine (1:2). In experiments 2 and 3 the treatments were (i) non cleaned control, (ii) cleaned after 1 h and (iii) cleaned after 3 h. The cleaning method in experiment 2 and 3 was pressure washing and scraping, respectively. Ammonia emissions were measured using wind-tunnels for 72 h. Cumulative NH3 emissions increased linearly with increasing urine N rate and emission factors ranged from 46% to 67% of urine urea-N applied and from 22% to 29% of total N applied. In experiment 2 and 3 the greatest reduction in cumulative NH3 emissions was obtained from pressure washing at 1 h which reduced emissions compared to the non-cleaned control by 91%. Pressure washing at 3 h reduced emissions by 80% while scraping after 1 h and 3 h reduced emissions by 78% and 54%, respectively. Farmers should be encouraged to clean their animal handling yards as soon as possible after use in order to maximise reductions in NH3 emissions from this source.

Background The enriched nitrogenous compounds in the dairy farms negatively affect the surrounding soil quality and air condition. The objective of this study is to investigate the transcriptomes of five key tissues involved in nitrogen metabolism and their changes under different diets to elucidate the molecular regulatory mechanisms of urine urea nitrogen (UUN) yield, one of the indicators of nitrogenous compound secretion of dairy cows. Results Cows fed high quality forage-based diet had lower UUN content and UUN yield, compared to those fed low quality forage (crop byproducts) based diets. From the transcriptomes of rumen, duodenum , jejunum , liver and udder, key driver genes and their UUN yield-associated functional gene networks were identified. In addition, the functional networks and expression of key drivers in various tissues (such as S100A8, CA1 and BPIFA2C in the duodenum; A2ML1, HMGCS2 and S100A12 in the jejunum; CYP2B6 and GLYCAM1 in the liver; APOE in the udder) changed in the cows fed crop byproducts based diet, which might be the predominant molecules to drive the increase UUN yield in these cows. Conclusion The information suggested that gut, liver and udder play important roles in regulating UUN yield, which could regulate nitrogen excretion waste. These findings provide fundamental information on future nutritional intervention strategies to reduce the UUN yield from dairy cows fed human inedible crop byproducts, which is vital for a sustainable and environmentally friendly dairy industry.

espanolIntroduccion: la restriccion proteica es fundamental en el manejo de la enfermedad renal cronica. Objetivo: evaluamos la utilidad de la medicion de nitrogeno ureico urinario como marcador de restriccion proteica. Metodos: participantes jovenes sanos fueron divididos aleatoriamente en dos grupos. Un grupo recibio una dieta con 30 kcal/dia/kg peso corporal y 1 g/proteina/dia/kg peso corporal y el otro recibio una dieta con la misma cantidad de calorias pero con 0,6 g/kg peso corporal de proteina. Al inicio, a los siete y a los 14 dias, los participantes respondieron una encuesta dietaria de recordatorio de 24 horas. Ademas, recolectaron orina de 24 horas y se les tomo una muestra aislada de orina al comienzo y a los 14 dias de la intervencion para medir creatinina y nitrogeno ureico. Resultados: cuarenta y un participantes de 29 ± 5 anos completaron el estudio. El grupo que consumio 0,6 g/kg de proteinas redujo su ingesta proteica de 0,88 ± 0,06 a 0,59 ± 0,05 g/kg/dia durante la intervencion. En este grupo se observo una reduccion significativa en la excrecion urinaria de nitrogeno ureico en 24 horas. No se observo tal reduccion en el grupo que consumio 1 g/kg de proteinas. La tasa de probabilidad de detectar una reduccion en la ingesta proteica en las encuestas dietarias, cuando se observaba una disminucion en la excrecion urinaria de nitrogeno ureico/mg creatinina de 24 horas, fue de 5,75 (intervalos de confianza de 95% = 1,29-25,55, p = 0,02). No hubo cambios significativos en la excrecion de nitrogeno ureico en las muestras aisladas de orina. Conclusion: las mediciones repetidas de nitrogeno ureico urinario en 24 horas son un marcador de restriccion dietaria de proteinas. EnglishBackground: protein restriction is the mainstay of dietary management of chronic kidney disease. Aim: to assess the usefulness of urine urea nitrogen measurement as a marker of protein restriction. Methods: healthy young participants were randomly divided in two groups. During 14 days, one group received a diet containing 30 kcal/kg body weight and 1 g protein/kg body weight and the other group received a diet with the same amount of calories and 0.6 g/kg of proteins. At baseline, seven days and 14 days, 24 h dietary recalls were answered by the participants. They collected 24 hour urine and provided spot urine samples at baseline and at the end of the intervention, to measure creatinine and urea nitrogen. Results: forty-one participants aged 29 ± 5 years completed the follow-up. According to 24h dietary recalls, the group receiving 0.6 g/kg protein reduced significantly the protein intake during the intervention from 0.88 ± 0.06 to 0.59 ± 0.05 g/kg/day. A significant reduction in 24 h urea nitrogen excretion was also observed in this group. In the group receiving 1 g/kg of protein, no significant changes in 24 h urea nitrogen excretion were observed. Among all participants, the odds ratio of observing a reduction in protein intake in the dietary survey was 5.75 (95% confidence intervals 1.29-25.55, p = 0.02), when a reduction in 24 h urea nitrogen excretion corrected by creatinine was observed. No changes were observed in urea nitrogen excretion in spot urine samples. Conclusions: repeated urea nitrogen excretion measured in 24 h urine samples can be a reliable indicator of dietary protein restriction.

Urine urea–creatinine ratio (U:C) often is used as an index of nutritional status of wild mammals, especially because urine can be collected from snow, providing a non-invasive index of nutrition. The rate of creatinine excretion has been assumed to be relatively stable; thus, creatinine concentration is used to normalize urea concentrations and control for dilution in snow. We present data from captive wolves (Canis lupus) to test how much variation in U:C is due to variation in urea vs. creatinine in relation to time since feeding. We found that U:C increases for ∼18 hours post-feeding but that this variation is primarily due to the 5-fold decrease in creatinine rather than the 2-fold increase in urea concentration. It is not clear what governs the variable creatinine concentrations in urine. Until a fuller understanding of this metabolite is achieved, ecological studies employing this nutritional index should report urea and creatinine values as well as the ratio. Physiological studies should ...

Renal urea conservation was evaluated in Corriedale ewes during late pregnancy and lactation. Glomerular filtration, renal plasma flow and urea clearance were significantly reduced both states compared with control sheep. Filtered load of urea and urine urea elimination were significantly reduced during lactation (−46% and −45%, respectively, vs. controls). No changes were noted in fractional excretion of urea. Therefore, Corriedale ewes restrict urine urea losses during lactation by reducing glomerular filtration. During late pregnancy, urea sparing is less marked. Key words: Renal functions, urea, pregnancy, lactation, sheep

Purpose: We ascertain the role of urea in urine and its probable effects on the polarizable behavior of bladder interfaces.Materials and Methods: Urine was systematically diluted, keeping overall volume the same. The methodology of nonequilibrium thermodynamics was used, which involves measurements of hydrodynamic permeability, electro-osmotic permeability, streaming potential and streaming currents, respectively.Results: Effective pressure terms (alpha 1) and polarizability terms (alpha 2) were computed, making use of higher order phenomenological coefficients, and their concentration dependence was examined. Abrupt changes in the values of alpha 1 and alpha 2 are supported by trends in higher order phenomenological coefficients.Conclusions: The polarizable behavior of the bladder is maintained up to certain concentrations of urea in urine and then it undergoes drastic changes. The role of the bladder in situations of improper functioning of the liver and diets without protein may provide an expl...

Nitrogen excretion was studied in the aquatic caecilian Typhlonectes natans by analyzing samples of the bathing medium over an 8-h period for total ammonia ($T_{amm}$: NH₃ + $NH_{4}^{+}$) and urea. Total ammonia was excreted at a rate of 0.35 μM · 10g⁻¹ · h⁻¹, while urea was excreted at a rate of 0.19 μM · 10g⁻¹ · h⁻¹. When excretion is expressed in molar equivalents of nitrogen, ammonia-N excretion was 0.35 μatm N · 10g⁻¹ · h⁻¹ while urea-N excretion was 0.38 μatm N · 10 g⁻¹ · h⁻¹. These latter values uwere not significantly different. Plasma $T_{amm}$ concentration was 1.3 mM, while plasma urea concentration was 4.4 mM Urine $T_{amm}$ concentration was 3.8 mM, while urine urea concentration was 2.7 mM. Partitioning $T_{amm}$ excretion between skin and kidneys found 1.11 μM · 10 g⁻¹ · h⁻¹ ammonia excreted across the skin. The kidneys contributed 0.09 μM · 10 g⁻¹ h⁻¹, or less than 8%. Skin urea excretion rate was 0.21 μM · 10 g⁻¹ · h⁻¹, while the kidneys accounted for 0.08 μM · 10 g⁻¹ · h⁻¹, or less than 28%.

Objective: to reveal the features of perioperative metabolic disturbances in patients with lung cancer after pulmonectomy and a possibility of their correction with perioperative «Standard» formula sipping and with postoperative intravenous cytoflavin. Subjects and methods. The paper presents the results of a prospective randomized study of the efficiency of correction of metabolic disturbances in patients with lung cancer with perioperative enteral «Standard» formula sipping (5 days before surgery and 12 days after surgery). The study was conducted in 326 men aged 36 to 68 years. Arterial blood metabolic parameters (glucose, lactate, and pyruvate) and daily urine urea were estimated. Results. There was an association of preoperative metabolic disturbances with body mass index (BMI). Inclusion of sipping into perioperative therapy did not exert a considerable impact on the cause of postoperative metabolic disturbances. Key words: lung cancer, pul-monectomy, body mass index, sipping, cytoflavin.

A kinetic assay for urine urea which employs the reaction with diacetylmonoxime at 37°C and undiluted urine was developed. Reaction conditions were optimized using the Monarch centrifugal analyser to produce an assay with the linearity to 450 mmol/L urea, and CVs of 2·3% and 2·5% within-batch and 4·6% and 3·3% between-batch at urea concentrations of 75·9 and 162·7 mmol/L, respectively; recoveries of 98·5% to 99·5% were obtained with the addition of the equivalent of 95 and 190 mmol/L urea. Comparisons were made with one urine urea method employing diacetylmonoxime with dialysis and two enzymatic methods which all involve a sample pre-dilution stage. The urine samples used for the method comparisons did not contain preservatives. However, a range of urine preservatives and a selection of possible interfering metabolites were shown to have no significant effect on the recovery of urea in the assay.

We have been developing a urine glucose level monitoring technique using near infrared spectroscopy in conjunction with the chemometric method aiming for the use of home health care. In this study, validity of the calibration models were assessed using urine samples from nine healthy male subjects. For the individual measurement, reasonable accuracy was obtained in predicting urine glucose level for each subject (mean value of standard error of prediction; 25.8 mg/dl, S.D.; 10.8 mg/dl), however, the accuracy decreased (around 60 mg/dl) when the calibration models were generated using data from multiple subjects. One of the causative factors seemed to be urine urea concentration level which may vary within very wide range (0-2000 mg/dl) under physiological condition, and therefore, it was suggested that any idea, e.g., classification of data by urea level, would be required for improving the accuracy.

The work aimed to evaluate the concentrations of plasmatic and urine urea, the balance of nitrogen compounds, and to estimate the protein requirements for maintenance. Equations recommended by the American and British systems were used in four bovine and four bubaline steers, with initial average weight of 461.19 ± 7.59 and 455.44 ± 7.85 kg for cattle and buffaloes, respectively, distributed into two 4 x 4 Latin squares. The treatments consisted of different levels of concentrate (0.0; 24.0; 48.0; and 72.0%) composed of cracked corn, soybean meal, mineral salt, and Tifton-grass hay. Each period lasted 21 days, being 14 for adaptation and seven for collection. Samples of feces and urine ( spot ) were taken to estimate the production of fecal dry matter and urine volume. Interactions were observed between the species for N intake (NC), urine-N (UN) g kg -0.75 and urinary urea (UU); no interactions occurred for fecal-N (NF), absorbed-N (NABS), UN (g d -1 ), balance of N (BN) and plasmatic urea (UP). Regardless of the difference observed between the species, the response variables increased linearly as functions of the growing levels of concentrate that resulted in positive BN. The estimate of metabolizable protein maintenance requirements for cattle and buffaloes differs between the American and British systems.

Twenty-four-hour urine urea nitrogen (UUN) collections are used to assess nitrogen loss in critically ill patients but are often difficult to obtain accurately. This prospective study compared 6- and 12-hour UUN collections with 24-hour UUN collections in critically ill patients receiving continuous nutrition support. ICU patients admitted from September 1999 through January 2003 who had UUN collections as part of routine care were recruited into the study. Patients were not receiving oral diets, were receiving continuous parenteral or enteral nutrition, and had indwelling urinary catheters. We excluded patients with hepatic or renal failure. Urine samples were collected every 6 hours starting at 6:00 am and kept refrigerated until the 24-hour collection was complete. Samples were analyzed using an automated urease enzymatic reaction. Samples were multiplied by a factor of 4 (6-hour samples) or 2 (12-hour samples) to estimate 24-hour totals and then compared with actual 24-hour totals. Twenty-four patients (18 men) completed the study; 21 patients had 6-hour samples (84 samples), and 24 patients had 12-hour samples (24 samples). Estimated 24-hour UUN from 6-hour (14.7-15.7 g/d) and 12-hour (15.2 g/d) samples did not differ significantly (p.5) from actual 24-hour totals (15.1 g/d). Shortened UUN collection times may be used to estimate 24-hour nitrogen losses in critically ill patients receiving continuous nutrition support.

LEARNING OUTCOME: To measure adherence of subjects prescribed a low protein diet using an individualized approach and frequent counseling. Individuals with early stage chronic renal insufficiency (CRI) may benefit from a low protein diet. We investigated the effects of exercise in protein-restricted subjects with CRI aged 48–79 y (mean=64±11 y) who were recruited from the greater Boston area who had a mean baseline serum creatinine of 2.9±1.0mg/dl and mean GFR of 32.9±27.3ml/min. Six subjects were prescribed a low protein diet (0.6g/kg adjusted body wt/d); the mean adherence period was 4±1 wks. Subjects were seen individually by a research dietitian 2x/wk for about 30–60 min/visit. Food records (FR) were recorded by patients 6 d/wk and analyzed using Nutritionist IV version 4.0. Twenty-four hour urine was collected 2x/wk to measure urine urea nitrogen (UUN) by the enzymatic method. FR and UUN showed a significant decrease in protein intake at the start of adherence period. Mean FR and UUN for protein intake were 82.78±26.14g/d (0.98 ± 0.13g/kg body wt/d) and 74.0±36.0g/d (0.86± 0.31g/kg body wt/d) respectively. At the end of adherence period, approximately 4 wks later, mean protein intake by FR was 39.89±11.49g/d (0.5±0.1g/kg body wt/d) and by UUN mean protein intake was 52.0±11.01g/d (0.64±0.05g/kg body wt/d); a decrease in habitual protein intake of 49% and 25% respectively as estimated from FR and UUN. Subjects underreported their food intake when total calories calculated from food records were compared to total energy expenditure from indirect calorimetry using a physical activity factor of 1.2. Degree of underreporting was most apparent in the subject with the lowest instrumental activities of daily living score. Subjects newly prescribed a low protein diet were able to reach the goal of 0.6 g protein/kg utilizing these techniques. Although a low protein diet may be desirable in early stage CRI, clinicians may experience difficulty with adherence due to lack of counseling time and frequent monitoring.

In response to fasting or fasting combined with water deprivation urine urea excretion declined sharply in normothermic ground squirrels (Spermophilus lateralis) when compared with laboratory rats. Intraperitoneal injection of urea equivalent to 0.3% of body weight failed to increase blood urea in 12-h fasted ground squirrels, and led to little urine urea excretion when compared with similarly treated rats. Collection of expired CO2 from fasted or fasted water-deprived ground squirrels that were urea loaded and injected with a tracer dose of 14C-tagged urea revealed a 1,000- to 1,500-fold greater 14CO2 expiration than controls. Treatment of fasted squirrels with antibiotics (penicillin, tetracycline, or sulfamethazine) to reduce intestinal microflora reduced expired 14CO2 to control levels. In fasted squirrels, drug treatment also enhanced urine urea excretion with values approaching those of controls. The results of these experiments point to the possibility of urea nitrogen recycling in nutritionally stressed ground squirrels.

Hypermetabolic burn patients are frequently in negative nitrogen balance despite provision of estimated caloric needs. We studied 18 thermally injured adult patients in order to evaluate the relationship of burn wound size to urea production and nitrogen balance. We selected data from 147 patient-days when the patients received 100 +/- 25% of their estimated caloric needs. Three significantly different burn size groups (by body surface area [BSA]) were identified by calculation of the catabolic index (CI): group 1, 0-10% BSA (CI = -0.1); group 2, 11-30% BSA (CI = 6.4); and group 3,31-60% BSA (CI = 10.5). The urine urea nitrogen (UUN) for groups 1,2, and 3 was 11.1, 18.9, and 25.3 gm/day, and nitrogen balance was 1.0, -3.9, and -5.8 gm/day, respectively. When nitrogen was given in a calorie:nitrogen ratio of 150:1, only those patients in group I were able to achieve positive balance. We conclude that large burn wounds are associated with increased ureagenesis and impaired nitrogen retention. The protein intake, at the customary calorie:nitrogen ratio of 150:1, may not provide adequate nitrogen to achieve equilibrium, even when energy demands have been met, in patients with burn wounds greater than 10% BSA.

This paper describes the preparation, properties, principles of operation and use of a new device, Immobilized Enzyme Pipette or Impette in routine determination of blood and urine urea. Clinical trials carried out in a medium sized hospital gave very reliable and reproducible results with a very high precision.

1. The sources of turbidity in directly nesslerized blood and urine filtrates have been discussed and a new method of nesslerization has been presented which eliminates turbidities. The new procedure has been compared in a quantitative manner with several methods. 2. A procedure for the determination of blood and urine urea and for urine ammonia has been presented, incorporating the new nesslerization technic.

A clinical rapid micro or super-micro method for urea is described, which will enable one to determine urea in a minute amount of urine, such as 0.1 c. c. or smaller amounts.

A new device that uses immobilized enzymes and is called an Immobilized Enzyme Pipette or ‘Impette’ is made by attaching disposable pipette tips made of polymeric nylon tubes containing enzymes attached covalently to their inner surface to the stem of an automatic, adjustable-volume pipette holder. This paper describes the preparation and application of this new device in research laboratories and as a routine analytical device in clinics. Other possible applications are also discussed.

In this paper we report a method to enable the Beckman BUN analyser to be used for urine urea nitrogen determinations. Satisfactory urine samples could be obtained by diluting the urine with 10 volumes of 0.85% saline. We also report our experience with the use of reagent prepared in house and with a modified pipette, to reduce the cost of using the instrument.

• Plasma and urine urea and creatinine levels were measured in 50 consecutive patients admitted to a coronary care unit. Forty of the patients had had myocardial infarction; their average plasma urea level increased substantially by the third day after admission, when 50% of the patients had an "abnormally" high plasma urea level. There was no change in plasma urea levels in ten patients who had not had a myocardial infarction. Results indicate that a rise in plasma urea level is common if not universal after myocardial infarction and is caused by either a fall in the glomerular filtration rate or an increased urea production rather than a mixture of the two. (Arch Intern Med1981;141:438-440)

Albumin synthesis rates in humans, based on precursor-product relationships have been estimated by two different methods, namely plasma urea method and urine urea method. The results of the two methods have been shown to correlate well. The advantages of urine urea method have been emphasised.

The accuracy of two-hour versus 24-hour urine urea nitrogen (UUN) determinations in critically ill patients was compared. A 24-hour urine collection for UUN determinations was obtained each day for five days in 20 patients who had been receiving parenteral nutrition at a constant rate for at least 36 hours. For each patient, the UUN value obtained from a two-hour sample was projected using the actual 24-hour urine output to determine an estimated daily UUN excretion. Creatinine clearance determinations were performed to evaluate the effects of impaired renal function on the correlation of two-hour and 24-hour UUN excretion. A significant correlation (r = 0.889) was found between the two-hour and 24-hour UUN excretions. However, in three patients with creatinine clearances less than 30 ml/min and two patients with gram-negative sepsis, correlations between two-hour and 24-hour UUN excretion were poor. Total urine volumes in the 20 patients varied considerably but did not affect the correlation between UUN determinations. A two-hour UUN determination may be a valuable tool for monitoring the nutritional status of critically ill patients. The rate of intravenous nutrition must be kept constant, however, to minimize diurnal variations in nitrogen excretion. Conditions such a shock, sepsis, or acute renal failure may limit the use of a shorter urine collection period for urea nitrogen determination.

In some children, small residual bladder volumes may predispose to urinary tract infections but current methods for determining small residual urine volumes are relatively inaccurate and impractical. A urine-urea exchange procedure was developed to determine full-bladder volume prior to voiding. Subtracting the volume voided from the full-bladder volume gives the residual volume. This procedure consists of injecting suprapubically a small volume of concentrated urea solution, and measuring the increase in osmolality; the larger the urine volume prior to the injection, the smaller will be the increase in urine osmolality following the injection. A mathematical error analysis to determine the overall statistical standard deviation of the full-bladder volume, the voided volume and the residual volume showed the standard deviation of each to be 0.929cc, 0.401cc and 1.33cc, respectively. With trials, using an in vitro laboratory model, the mean error of the full-bladder volume was 1.1cc and the mean error of the residual volume 1.14cc. In vivo dog experiments confirmed that the procedure is safe and practical. Clinical trials have been started.

The present study deals with the effect of feeding diets containing various concentrations of whole meat on the amount of urea in the urine and blood and the urea (Addis) ratio, urea excreted/blood urea in partially nephrectomized, unilaterally nephrectomized and intact rats. The experimental procedure, the experimental diets and abbreviations were outlined in a previous paper. 1 The data for all animals excreting less than 50 per cent of the urea solution administered were excluded. The previous data have been supplemented by values obtained at frequent intervals in individual animals. RESULTS The effect of various concentrations of whole dried meat on the amount of urea in the blood and urine and on the urea ratio, urea excreted per hour X 100, of partially nephrectomized and control aniurea in 100 cc. blood mals (unilaterally nephrectomized and intact) is shown in chart 1. Five phases of renal function are

Temperature regulation and water economy were studied in two species of spiny mice, Acomys russatus and Acomys cahirinus. Both species share the same desert habitat in Israel, but A. russatus is active during the day and A. cahirinus is nocturnal. It was shown that A. russatus was better able to maintain its normal body temperature (TB) when exposed to high ambient temperatures (TA) and survived temperatures as high as 42.5°C. On the other hand, TA 40°C was lethal to A. cahirinus. Mean minimal metabolism of A. russatus was 34.5 per cent lower than the value predicted from body weight, and that of A. cahirinus was 13.5 per cent lower. A. russatus had no thermoneutral zone, oxygen consumption being minimal at TA 30°C. A . cahirinus had a narrow thermoneutral zone between 27 and 32.5°C TA. High ratios of evaporative water loss per milliliter of oxygen consumed were measured in both species; at 30°C it was 2.3 mg H2O/ml O2 in A . russatus and 1.9 mg H2O/ml O2 in A. cahirinus. When restrained at 30°C, 60 to 70 per cent of evaporation was from the skin. Maximum urine urea concentration in both species was 4700 to 4800 mM, among the highest recorded for mammals. Maximum chloride concentration was higher in the urine of A. russatus and amounted to 1500 mN, almost twice that of A. cahirinus. Accordingly, the capacity to utilize salt solutions for drinking was higher in A. russatus, which could drink sea water or NaCl solution as concentrated as 0.9 N. At 30°C, both species, when deprived of drinking water, failed to survive on a diet of barley. A. russatus could be considered physiologically better adapted for a diurnal existence than A. cahirinus, both in its ability to cope with high ambient temperatures and in its capacity to derive water from salty, succulent plants.

This is the first of a short series of papers, the outcome of an attempt to draw quantitative structural deductions from functional results. The few methods used are discussed and criticized only in reference to the question as to whether the results give information in regard to the amount of secreting tissue in the kidney. This narrow point of view has been adopted because the purpose of the inquiry is entirely utilitarian and clinical. All manifestations of renal function have an intrinsic interest from the standpoint of physiology, but it is maintained that only those from which we can draw quantitative conclusions about the amount of tissue in the kidney are of immediate and practical clinical importance. Such an idea is foreign to nearly all the recent work on this subject. Nevertheless, from the time of Bright up to about the beginning of the last decade, the hope that functional

Many attempts have been made in recent years to develop a satisfactory test for the urea function of the kidney. Ambard presented his coefficient of urea excretion and F. C. McLean introduced the McLean index, which utilized the principles of Ambard's formula but simplified them. H. MacLean and de Wesselow1brought out the urea concentration test. Addis2studied the ratio between the one hour urine urea and the urea in 100 cc. of blood and Rabinowitz employed the urea concentration factorVarious investigators have shown that urea excretion in normal persons depends on the blood urea concentration as well as on the renal efficiency and also that the concentration of urea in the urine in normal persons can be increased indefinitely, under conditions compatible with life, by increasing the blood urea concentration. It has been further proved that the volume of water excreted has only a slight effect on urea excretion