438 



GENERATION. 



The following table is intended to exhibit a 

 synoptical view of the various forms of the 



reproductive process 

 classes of animals. 



occurring in different 



Fissiparous 



Non-sexual . . . . 



i 



Gemmiparous . . 



Sexual 



! Parent splits, each part a new animal. 

 1. Transverse. 

 2. Longitudinal. 

 3. Irregular. 

 Parent splits and discharges the young. 

 $ Budding upon the parent stock. 

 ^ Separated buds. Gemmae or sporules. 



1. On all parts of the body. 



2. On one part or organ only. 

 Hermaphrodite. Both sexual organs on one individual. 



1. Self-impregnation. 



2. Mutual impregnation. 

 Oviparous, laying eggs which are hatched. 



1. External fecundation. 



2. Internal fecundation. 

 Ovo-viviparous. Eggs hatched within the 



maternal body. 

 Mammiferous, suckling the young. 



1 . Monotrematous. 



2. Marsupial. 



3. Placental or strictly vivi- 



parous. 



Dioecious. 



III. REPRODUCTIVE FUNCTION IN MAN AND 

 THE HIGHER ANIMALS. 



1. Sketch of this function in man. In now 

 proceeding to a more detailed account of the 

 function of generation, our description must be 

 confined to the process of reproduction in the 

 human species and in those animals which are 

 most nearly allied to man. 



The following may be mentioned as the 

 principal steps of the reproductive process in 

 the female of the human species. 



The human offspring is derived from an egg 

 like that of all the more perfect animals. The 

 egg is gradually formed in the Graafian vesicle 

 of the ovary at the period of maturity. In 

 productive sexual union the vagina and uterus 

 receive a certain quantity of the male seminal 

 fluid, and a series of changes are induced in 

 the female generative system which have the 

 effect of dislodging one or more ova from their 

 residence in the ovary, and of bringing these 

 ova into contact with the seminal fluid, in 

 order that they may be fecundated or rendered 

 fruitful. The mechanism of the discharge of 

 the ova is the following. The Graafian vesicle 

 swells, and bursts at its most prominent part. 

 The ovum escaping from its interior is received 

 by the fimbriated cavity at the commencement 

 of the Fallopian tube, along which tube it 

 gradually passes until it reaches the interior of 

 the uterus, where it arrives probably in ten or 

 twelve days after sexual union. There is every 

 reason to believe that before the ovum reaches 

 the uterus it has already been exposed in some 

 part of the genital organs to the influence of 

 the male semen, and that it is consequently 

 fecundated. \\ e shall have occasion after- 

 wards to inquire more minutely into the place 

 and manner of this fecundation. The female 

 is now said to have conceived or to be impreg- 

 nated, and the ovum to be fecundated. We 

 shall endeavour, for the sake of clearness, to 

 bring the history of the steps of this process 



under the three distinct heads of, first, the 

 changes of conception as regards the female, 

 secondly, the process of fecundation as relating 

 to the male, and thirdly, the effects of the union 

 of the male and female product. 



Before the ovum reaches the uterus a change 

 has already commenced in the interior of that 

 organ, which in its farther progress has for its 

 object to bring about an organic union between 

 the uterus and the fcetus with its coverings. The 

 minute embryo soon becomes visible in the 

 ovum, has envelopes formed over it which 

 become connected with the lining membrane 

 of the uterus, and as it advances in growth 

 continually receives a supply of nourishment 

 from the bloodvessels of the uterus. It is 

 nourished in this way during the whole of its 

 intra-uterine life, at the termination of which 

 the child is brought into the world or born, 

 being expelled from the uterus by those pain- 

 ful efforts and contractions of the uterus con- 

 stituting parturition or labour. The child is 

 now capable of being nourished by digestion 

 of food in the stomach, independently of 

 any organic connexion with the mother, and 

 breathes air by its lungs. Although all or- 

 ganic connexion, however, between the mother 

 and child is now dissolved, yet the infant is 

 for a time dependent on the mother for nou- 

 rishment, receiving by sucking from the mam- 

 ma; the milk, which it assimilates by its own 

 independent powers. In the present article 

 our object is to describe only the processes of 

 conception and fecundation, referring to the 

 article OVUM for an account of the growth of 

 the foetus, and to the articles UTEKUS, OVARY, 

 &c. for the more minute anatomical and 

 functional relations of these organs in the 

 unimpregnated and impregnated states. 



Organs of reproduction. The organs of 

 reproduction in both sexes are frequently divi- 

 ded by anatomists into external and internal, 

 according as they are situated more or less near 



