OF GENERATION.
IF we have found it difficult to account for the series of actions which constitute the functions .that have lately passed under our review, still more so shall we find it to explain the mysterious operation by which a succession of individuals is produced for the continuance of the spe cies. It will not be necessary for us to give any descrip tion of the appropriate organs, nor of the process by which it is accomplished; we shall confine ourselves to a detail of some of the more important changes which take place in the production of the foetus, to which we shall add a few remarks upon the theories that have been proposed to explain these changes.
In all those animals, whose structure and functions bear a general resemblance to the human, generation is per formed by the concourse of the two sexes, the office of the male being to introduce a portion of the fluid which is secreted by the testes, into a part of the body of the fe male, appropriated for its reception. It is probable that the emission of the semen from the male may be referred to the same kind of action by which secreted fluids are ordinarily discharged, the excitement of the termination of the excretory duct. But the series of actions which take place in the female are much more complicated, and are involved in much more obscurity. She has not only to contribute her share of the matter which may serve for the formation of the embryo, but she has likewise to pro tect and nourish it during the foetal state, until its own organs have acquired sufficient maturity to support its in dependent existence. This appears to be the result, in part, of a certain operation which is performed by the vas etilar system of the mother, and in part by the production of certain membranes which essentially belong to the foetus, and are attached to the parent during a limited pe riod only, for the purpose of keeping up the communica tion between them. In order to furnish the rudiments of this temporary apparatus, the female is provided with an organ called ovarium, from the analogy of the oviparous animals, and by a complicated and hitherto inexplicable connexion between this part and the entrance of the se minal fluid into the uterine system, the first change which occurs in the female is the production of a small glandu lar body in the ovary, which, after a certain interval, is discharged from its nidus, and is transmitted along the Fallopian tube into the cavity of the uterus. At this pe
riod the quantity of blood sent to the uterus is augment ed, so that both the embryo and the uterus itself gradu ally increase in bulk until their final separation takes place. But although we may conceive, that what has now been stated constitutes the essential part of the pro cess, there are many points respecting it which are very obscure. In the first place, it may be assumed as a ne cessary part of the operation, that the female must contri bute, along with the male, to the materials of the foetus, yet we have no knowledge of any secretion which can serve for this purpose, or of any organ by which it is fur nished, unless we suppose it to compose a part of the ve sicle which produces the connecting membranes. Ano ther question which has been much agitated respects the mode in which the male secretion acts upon the female ovary ; is it brought into actual contact with the part, or does it produce some change in the uterus, which is pro pagated to its appendages, and operates upon them ? :Many observations, as well as direct experiments, have been performed for the purpose of ascertaining this point ; the result of which renders it probable, that the formation of the vesicle does not require the immediate application of the semen. It appears, on the contrary, that the evo lution of the vesicle and its transmission into the uterus depend upon a remote action, propagated to the part, which causes the succession of changes to take place in their clue order.