"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. 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 toward the sides, and the heart exhibits its external form, bearing a close resemblance to that in an 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 sacks, 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-half to two inches long, the head forming more than one-third of the whole. At the end of THREE MONTHS, the eyelids are distinct but shut; the lips are drawn together; the forehead and nose are clearly traceable, and the organs of generation prominent. The heart beats with force; the larger vessels carry red blood; the fingers and toes are well defined, and the muscles begin to be developed.