Helen Idleson, M. D., in the _Med. Wochenschrift_, sums up the results of her investigations as follows: “1. The duration of pregnancy amounts to 278 days, or nearly 40 weeks. 2. The sex of the infant influences the duration, this being longer in female infants. (?) 3. The heavier the child, the longer is the duration. (?) 4. The duration is longer in multipara than in primipara. 5. The younger the woman the longer is the duration. 6. The duration is longer in married than in unmarried women. 7. The first movements of the child are felt, on an average, on the one hundred and thirty-fifth day, but later in primipara than in multipara. “The _growth of the embryo_ after fecundation is very rapid. On the _tenth_ day it has the appearance of a semi-transparent, grayish flake. On the _twelfth_ day it is nearly the size of a pea, filled with fluid, in the middle of which is an opaque spot, presenting the first appearance of an embryo, which may be clearly seen as an oblong or curved body, and is plainly visible to the naked eye on the _fourteenth_ day. The _twenty-first_ day the embryo resembles an ant or a lettuce-seed; its length is from four to five lines and its weight from three to four grains. Many of its parts now begin to show themselves, especially the cartilaginous beginnings of the spinal column, the heart, etc. “The _thirtieth_ day the embryo is as large as a horse-fly, and resembles a worm, bent together. There are as yet no limbs, and the head is larger than the rest of the body. When stretched out it is nearly half an inch long. Toward the _fifth_ week the heart increases greatly in proportion to the remainder of the body, and the rudimentary eyes are indicated by two black spots turned toward the sides, and the heart exhibits its external form, bearing a close resemblance to that in the adult. “In the _seventh_ week bone begins to form in the lower jaw and clavicle. Narrow streaks on each side of the vertebral column show the beginning of the ribs. The heart is perfecting its form, the brain enlarging and the eyes and ears growing more perfect, and the limbs sprouting from the body. The lungs are mere sacs, about one line in length, and the trachea is a delicate thread, but the liver is very large. In the seventh week are formed the renal capsules and kidneys. “At _two months_ the forearm and hand can be distinguished, but not the arm; the hand is larger than the forearm, but it is not supplied with fingers. The distinction of sex is yet difficult. The eyes are prominent. The nose forms an obtuse eminence. The nostrils are rounded and separated. The mouth is gaping and the epidermis can be distinguished from the true skin. The embryo is from one and a half to two inches long and weighs from three to five drachms, the head forming more than one-third of the whole.