NS bile, therefore, the principal object of the present article is to describe the process of generation in Man and the higher N'ertehrated animals, it will be necessary and proper for us to allude also to the reproductive function as it is performed in all the various members of the animal series; for in this, as in other de partments of Physiology, the more complicated forms of the process derive much illustration from the study of the more simple, and we may hope thus more fully to point out the general importance of the functions now under consideration.
We purpose to follow an arrangement adapted chiefly to the consideration of Human Generation. In all the animals in which dis tinction of sex subsists, the male and female organs subservient to reproduction must co operate for the completion of the generative process ; and in the greater number of the more perfect animals, as also in Man, the two kinds of sexual organs being placed on separate in dividuals of the same species, the concurrence of both these individuals, or of both male and female parents, is necessary for the for mation of tire fruitful products from which the offspring proceeds. The circumstances, then, which give rise to the union of the sexes, and the phenomena which accompany that union, form some of the topics of the present article. The product of fruitful sexual union in all animals is one or more eggs, from each of which, under the influence of certain favourable circumstances, different in different tribes, the young animal is produced by an intricatepro eess of vital growth. The greater part of the substance composing the egg is furnished by the female parent: but this egg of the female would he wholly barren, or would Dot undergo any of those changes by which the young animal is formed, unless it received in some way or other the influence of the product of the generative organs of the male; and the egg formed by the female may be regarded as im perfect until the change now alluded to has been effected in it. It is then said to be
fecundated or rendered, fruitful by the semen of the male. The mode of formation of the egg and seminal matter, the mode of their Separation from the place of their formation, the structure and properties of each of these products, the mariner in which they are brought together, the influence which they exert upon one another, and the consequent result in the production of the young, con stitute the principal remaining topics which fall to be discussed by us at present. In this article our attention must chiefly be confined to such operations or functions of the male and female parents as are preliminary to or necessary for the formation of a ripe and fruit ful ovum that is, an egg capable of giving birth to a new animal the same as either of its parents, when placed in those circumstances which are favourable to its evolution. It is not intended to speak in this place of tire changes of the ovum itself in which the for mation of the young animal consists : the consideration of these is reserved for the article Ov sr.
Before treating in detail of Human Gene ration, we introduce some remarks on the nature of the reproductive function in general, and a sketch of the principal varieties of the forms it assumes in different classes of ani mals.