Page:The Works of William Harvey (part 1 of 2).djvu/586

 nearly perfect, in one case in the right in another in the left horn of the uterus ; in twin cases in both horns.

At this time, too, the male embryo is readily distinguishable from the female by means of the organs of generation. These parts are also very conspicuous in the human embryo, and make their appearance at the same time as the trachea.

Males and females are met with indifferently in the right and left horn of the uterus. I have, however, more frequently found females in the right, males in the left horn ; and I have made the same observation in does that carried twins, as well as in the sheep. It is certain, therefore, that the right or left side has no appropriate virtue in conferring sex ; neither is the uterus, nor yet the mother herself, the fashioner or framer of the foetus, any more than the hen is of the pullet in the egg which she incubates. In the same way as the pullet is formed and fashioned in the egg by an internal and inherent agent, is the foetal form produced from the uterine ovum of the hind and doe.

It is indeed matter of astonishment to find a foetus formed and perfected within the amnion in so short a space of time after the first appearance of the blood and punctum saliens. On or about the 19th or 20th day of November this punctum first becomes visible; on the 21st the shapeless vermiculus or maggot that is to form the body of the future animal is per- ceived ; and in the course of from six to seven days afterwards a foetus so perfect in all its parts is seen, that a male can be distinguished from a female by the organs of generation, and the feet are formed, the hooves being cleft, the whole having a mucous consistency and a pale yellowish colour.

The substance of the uterus begins to be extenuated imme- diately after the appearance of the embryo ; contrary to what takes place in the human female, whose uterus grows every day thicker and fleshier with the advancing growth of the foetus. In the hind and doe, on the other hand, the more the embryo aug- ments the more do the cornua of the uterus assimilate themselves to the intestines ; that horn in particular in which the foetus is contained looks like a bag or pouch, and exceeds the opposite one in dimensions.

The ovum or conception, thus far advanced, and with its in- cluded foetus perfectly distinct, has still contracted no adhe-