SummaryMyxœdema is characterised by the total absence of a hypertensive response to adrenalin. Under influence of the treatment with thyroïdine the sensibility to adrenalin is increased in direct relation to the degree of impregnation of the organism with thyroïd hormone. These facts support the opinion that the thyroïd hormone determines the sensibility of the organism to the activity of the orthosympathetic system.