Summary. Blood flow to the testis, haemoglobin oxygen saturation and testosterone concentration in arterial and venous testicular blood vessels were studied in Texel rams in the breeding and non-breeding season.Blood flow in the proximal and distal testicular artery was measured electromagnetically. The mean flow in the proximal testicular artery was 18\m=.\5 ml/min and in the distal testicular artery 7\m=.\5 ml/min, and there was no detectable seasonal influence.Haemoglobin oxygen saturation and testosterone concentration were measured in the saphenous artery and vein, the distal testicular artery and vein, and in the proximal testicular vein. The haemoglobin oxygen saturation in the proximal testicular vein was significantly higher than in the distal testicular vein in both seasons. The mean testosterone concentration was significantly lower in the proximal testicular vein than in the distal testicular vein in both seasons. Based on haemoglobin oxygen saturation and testosterone data, it was calculated that between 28 and 46% of the testicular arterial blood was bypassing the testis and was directly flowing through arterio-venous anastomoses towards the pampiniform plexus in the spermatic cord of conscious rams. In anaesthetized rams 55 and 64% of the blood was flowing directly from the testicular artery to the pampiniform plexus based on blood flow data.Transfer of testosterone and oxygen by passive diffusion from the testicular artery to the pampiniform plexus and vice versa in the spermatic cord was not detected.

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The antiarrhythmic potency of Mg has been described repeatedly since 1935, both as a factor in human disease and in animal experiments. Nevertheless, this therapeutic efficacy is rarely mentioned in textbooks. Both the pharmacological effect of Mg and the correction of Mg deficiency have been used in treatment of digitalis toxicity, variant angina, Torsades de Pointes, as well as in arrhythmia of unknown origin. Mg-deficiency can be caused by malabsorption or by excessive urinary loss. Both situations can occur on a congenital basis. The most frequent cause is probably alcoholism. Iatrogenic factors include digitalis, diuretics, gentamicin, as well as cisplatinum, which appreciably enhance urinary Mg loss. Correction of Mg-deficiency by parental and/or oral administration should lead to recovery. If the cause of the deficiency can be eliminated, once the deficit is repaired it may be acceptable to discontinue the supplement. However, the cause is often multifactorial, requiring further evaluation and treatment.