The various methods of measuring the nutritive value of proteins have been frequently reviewed (Chick, 1942;Mitchell, 1944;Allison, 1949 A method is described here, whereby seven proteins can be tested simultaneously in 10 days, using thirty-two rats and involving no N estimations other than on the food. The method is based on the formula already discussed (Bender & Miller, 1953 a). In principle the values obtained are the same as those obtained by the Thomas-Mitchell procedure, being a measure of that proportion of the food N eaten retained by the test animals. EXPERIMENTALAnimals. Rats of our hooded strain were used in all the experiments. T h e animals were weaned at 21 days at a weight of about 35 g, and fed for I week on stock diet so that they weighed 50-60 g at the beginning of the experiment.Chemical analyses. Body water was determined after killing the rats with chloroform. Incisions were made into the skull, thoracic and body cavities, and the carcasses were dried to a constant weight at 105' (48 h). Intestinal contents were included. N was determined by the Kjeldahl method. Small rats, of less than 15 g dry weight,were completely digested with 10 ml. conc. H,SO,/g dry matter and 20 g catalyst (2 g SeO,, 2 g CuSO,. 5H,O, 16 g K,SO,). T h e dried carcasses of the larger rats were pounded in a mortar and 10-15 g portions digested. The large size of the portions compensated for any lack of homogeneity as shown by the agreement between duplicate digestions. Samples of this size, especially those rich in fat, frequently froth violently during digestion, but this frothing was avoided by maintaining the digestion mixture at 120' for 2 h before strong heating. T h e digested material was finally diluted for the micro-estimation of ammonia (Markham, 1942

The growth method of comparing the nutritive value of proteins, namely the estimation of protein efficiency ratio (P.E.R.) has long been popular because of its simplicity despite its well-known drawbacks (Mitchell, 1944).Among the more serious disadvantages of this method are: (a) no allowance is made for maintenance requirements of the test animal, (6) the result varies with food intake, and (c) the assumption that the gain in body-weight is indicative of the protein tissue laid down is not always valid.A modification is described whereby a control group of animals fed on a protein-free diet is included in the experiment, and the difference between the weights of this group and the test group is used in the calculation instead of merely weight gain. This procedure allows for maintenance requirements and also permits the evaluation of poor proteins which do not promote growth (and of which, consequently, P.E.R. cannot be measured). The results obtained are independent of food intake. T h e third criticism mentioned above is shown to be of minor significance under our experimental conditions. EXPERIMENTAL Animals and diets. The rats and diets and amino-acid mixtures were as described previously (Bender, 1956).Body water. The whole carcasses, without evisceration or cleaning of the gut, were dried to constant weight in a hot air oven at 1 0 5~.

There has been considerable interest recently in the relationship between depression and the workplace. This interest is driven by the growing recognition that depressive disorders are highly prevalent in the workplace and have an enormously negative impact on performance, productivity, absenteeism, and disability costs. A variety of clinical research with occupational-related samples has helped to define those at risk for depression and has led to a better understanding of the overlap of the construct of clinical depression with more longstanding occupational health and organizational psychology models such as stress, burnout, and job satisfaction. From an employer perspective, depression's impact remains largely unmitigated due to stigma, uncertainty about treatment's cost effectiveness, and lack of effective interventions delivered in a workplace setting. Progress in these areas is reviewed with suggestions for future directions.

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