5. This is the position of all the parts: the first and last part adjoining the shell is the membrane of the egg, not the membrane of the shell, but beneath this. This contains the fluid white; within this is the young bird, and a membrane surrounding it, and separating it from the fluid; beneath the embryo is the yolk, to which one of the veins extends, and the other to the white which encloses it. A membrane containing a fluid resembling sanies encloses the whole, and then another membrane which surrounds the embryo itself, as I observed, and separates it from the fluid. Below this the yolk, enclosed in another membrane, which is reached by the umbilical cord from the heart, and the great vein, so that the embryo does not appear to be in either of the fluids.
6. About the twentieth day, if the hatching has been delayed beyond this period, the young bird is able to chirp when moved externally, and if the shell is taken off, by this time also it is downy. The head is placed over the right leg upon the side, and the wing is over the head. At this period the chorion-like membrane is visible, which is united with the lowest membrane of the shell, to which one of the umbilical cords passes, and the young bird is complete. The other chorion-like membrane is also visible, enclosing the yolk. To this the other umbilical cord extends. Both of these cords are attached to the heart and the great vein. At the same period the cord which is attached to one chorion falls off, and is separated from the animal, but the one which passes to the yolk remains suspended from the young bird by a thin bowel, and a considerable portion of the yolk is contained in the young bird, and some of it is found in the stomach.
7. At this period also they eject an excrementitious matter into the external chorion, and contain it in the stomach. The external excrement is white, the internal yellow. At last the yolk, which has been continually wasting and advancing, is entirely taken up and enclosed in the young bird. So that portions of it may be observed in the intestines of birds if they are dissected on the tenth day after exclusion from the egg. But it is set at liberty from the navel, nor does any communication remain, but the whole is separated. About the before-mentioned period the young bird sleeps, but it stirs itself, and looks up, and chirps when it is touched, and the heart swells up with the navel, as if the embryo were breathing. This is the manner of the development of the chick in the egg.