The effects of local applications of chloride and sulphate of magnesium upon the centers in the medulla compared with those of sodium chloride

The three salts were applied in molecular solutions to the exposed medulla oblongata of rabbits. Both salts of magnesium abolished sooner or later all the functions depending upon the centers located in the medulla, the average time until a complete effect took place being fifteen minutes. Respiration stopped and blood-pressure came down to forty or thirty millimeters of mercury and sometimes even lower. Strong stimulations of the sciatic nerve had now no effect upon blood-pressure. After curarin and strychnin were given stimulation of the sciatic caused some rise (spinal centers). Electric stimulation of the superior laryngeal nerves or mechanical stimulation of the pharynx caused no deglutition. Injection of fluid into the œsophagus caused no contraction of that organ (no secondary peristalsis). Intravenous injection or local application of calcium did not restore these functions. In a few cases spontaneous respiration returned after a few hours of continuous artificial respiration.

Sodium chloride had no depressing effect; on the contrary, there was a moderate stimulating effect upon the respiration and blood-pressure. There was a strikingly stimulating effect upon the center of deglutition; for eight or ten minutes the animal had to swallow every ten or fifteen seconds.