Toxins from the fetal syncytium appear to be another cause of the vomit. The syncytium is a mass of protoplasm without cell demarkation but with nuclei scattered throughout the substance. Sometimes this embryological cellular material starts to grow after the manner of a cancer, and then it is very malignant (_syncytioma malignum_), but its connection with the pernicious vomit of pregnancy is more theoretical than established. In physiological conditions the toxins in the blood are neutralized by the secretions of the ductless glands of the body, and in pregnancy probably these same glands by intensified activity effect the same result. Injection of blood serum taken from healthy pregnant women has cured cases of toxemic pernicious vomit, and this makes the theory much more probable. To diagnose the etiology of pernicious vomiting is not always easy. We must decide first whether the emesis is really pernicious or not; secondly, we have to determine whether or not it is due to the presence of the fetus; thirdly, we are to differentiate the primary and adjuvant causes for intelligent treatment. The age of the fetus must be known to determine whether we may licitly interfere so as to remove the fetus from the uterus if necessary, in medical opinion, to do so. Trousseau emptied the uterus of a woman to stop her pernicious vomit, but she died, and at the autopsy he found a cancer of the stomach. Caseaux discovered tubercular peritonitis in a woman who had died after a diagnosis of hyperemesis gravidarum; Beau, tubercular meningitis in a like case. Williams of Johns Hopkins University stopped a very grave case of pernicious vomiting in a neurotic woman merely by telling her of the dangers of artificial abortion. There is no settled mortality percentage in hyperemesis gravidarum because so much depends on diagnosis and treatment. Braun, in 150,000 obstetrical cases, never had a death from pernicious vomit; others have a mortality of 40 per cent.