=Abderhalden’s test= is a serum reaction based on the well established principle that the introduction into the blood of an organic foreign substance leads to the formation of a ferment to destroy it. Abderhalden’s plan was to discover whether the blood of a pregnant woman contained a ferment capable of destroying placental protein. It is a very complicated test, and subject to many inaccuracies and numerous sources of error. At the same time, the main features of this reaction have been confirmed, and when it is worked out, it will be of immense value not alone in early uterine pregnancies, but in extrauterine pregnancy. This view very properly demands that pregnancy be regarded as a parasitic disease. It is practicable as early as the sixth week to make a diagnosis, and it only fails in possibly ten per cent of the cases. The negative test is equally definite as eliminating pregnancy. =Sixteenth Week.=—Morning sickness and urinary symptoms have disappeared but amenorrhœa remains. Enlargement of the breasts is noticeable, as well as the increased pigmentation. The uterus begins to rise above the symphysis as an elastic, somewhat ill-defined, boggy mass. The cervix is softer. The characteristic dull lavender coloration of the vulvar mucous membrane is now evident. It is due to the congestion and is called Jacquemins’ sign. =Two New Signs.=—Irregular, painless contractions of the uterus (Braxton Hicks’ sign), and ballottement. The contractions of Braxton Hicks now become more easily palpable. Ballottement consists in the detection in the uterus of a movable solid body surrounded by fluid. In a standing position, the fœtus rests in the lower part of the uterus, just above the cervix. The woman stands with one foot on a low stool, and two fingers of one hand are pushed into the vagina until they touch the cervix, the other hand is placed on the fundus. A smart upward blow by the internal hand is transmitted to the fœtus, and it can be felt to leave the cervix, strike lightly the tissues underneath the external hand, and return to the cervix. It is simulated by so few things, and so rarely, that in practice it must be regarded as a positive sign. During the second half, the subjective symptoms are of minor importance since unmistakable evidence is furnished by the physical signs. The symptoms of this period are mostly discomforts. Increased intraabdominal pressure brings on edema of the feet, cramps in the legs, varicose veins of the legs and vulva, dyspnœa, and palpitations. =Twenty-sixth Week.=—About the twenty-sixth week, or, at the end of the sixth calendar month, the hypertrophy of the breasts, the presence of secretion, and the marked pigmentation are unmistakable. The abdominal protrusion is now clearly visible, and the fundus will be found at the level of the upper border of the umbilicus. Spontaneous fœtal movements appear and may be felt by the palpating hand.