SummaryThe authors relate the results of S. D. A. of Proteins measurements in about 400 subjects.The technic of the measurements and the expression of the results are the objects of a critical examination.Measurements were made in consecutive series on 3 patients.With the technics used, normal patients show a S. D. A. value varying from 6 to 14 for women, from 10 to 18 for men.An abnormal low value was found in severe diabetes insipidus, in severe hypothyroïdism in the adult, in the adiposogenital syndrome of diencephalic origin.There is an obvious increase of S. D. A. values in hyperthyroïdism and its sympathicotonic sequels. These values are not related to basal metabolic rate, but to the neurotonic manifestations.In Simmond’s disease, in pseudo-syndrome of Simmonds, which is accompanied by functional pituitary insufficiency, and in pituitary sterility, there is also an important depression, even an absolute lack of the S. D. A. of proteins.In the so called«pituitary type»of obesity, in water and salt obesity, in pituitary thinness, in psychasthenia, the average values are obviously under the normal.We never noted an abnormal increase, neither in gigantism, nor in acromegaly, where pituitary hyperactivity may be incriminated.In cases of menopause with endocrinologic troubles and in cases of castration, where the hypophysis equally shows an intense hyperactivity, the S.D. A. rates are normal or low.Thyroïd extracts raise the S. D. A. rate but in certain cases, rest, high food supply and pituitary gonadotrophic extracts, may have the same effect. Under treatment, the S. D. A. rate rises when the nutritional or endocrinologic or nervous or psychic state of the patient improves.In conclusion, the S. D. A. of proteins does not seem to be directly influenced by the various pituitary hormones, the thyreotrophic, gonadotrophic, diabetogenic or growth hormones.The measurement of the S. D. A of proteins is not a test of deficient or excessive activity of the hypophysis. It reflects the functional state of the automatic nervous system, i.e. of a coplex apparatus influenced by the endocrines.