ACTION OF THE FEMALE. 445 



nature ; the Will having no power either to effect or to restrain it. 

 The stimulus is given by the friction of the surface of the Glans Penis 

 against the rugous walls of the Vagina ; the sensibility of the organ 

 being at the same time much increased, by the determination of blood 

 to it. The impression is at last sufficiently strong to produce, through 

 the medium of the lower part of the Spinal cord (which is the gangli- 

 onic centre of the circle of afferent and efferent nerves connected with 

 this organ), a reflex contraction of the muscles surrounding the Vesi- 

 culse seminales. These receptacles discharge their contents (which 

 consist partly of the Spermatic fluid, and partly of a secretion of their 

 own) into the Urethra; and from this they are expelled, with some 

 degree of force, and with a kind of spasmodic action, by its own Com- 

 pressor muscles. Although the sensations concerned in this act are 

 ordinarily most acutely pleasurable, yet there appears to be sufficient 

 evidence that they are by no means essential to its performance ; and 

 that the impression conveyed to the Spinal cord may excite the con- 

 traction of the Ejaculator muscles, like other reflex operations, without 

 producing sensation ( 394). 



3. Action of the Female. 



791. The share of the Female in the Generative act is greater than 

 that of the Male; for she not only furnishes, in the "germ-cell," a 

 product which is as essential as that supplied by the " sperm-cell" for 

 the first formation of the germ ; but she also supplies it with the mate- 

 rials which it requires for its development, up to the condition in which 

 it can support its own life. The mode in which this is accomplished, 

 is essentially the same with that in which the process is effected in 

 Plants. In certain parts of the female structure are developed pecu- 

 liar bodies termed ova ; which contain, not merely the germ-cells, but in 

 addition a store of nutriment adapted to supply the wants of the germ. 

 The fertilizing influence finds its way into these ; and the germs thus 

 produced begin to grow at the expense of the material with which they 

 are surrounded. This, as already pointed out, may enable the embryo 

 to develope itself, without any further assistance (save a warm tempe- 

 rature) into the form it is permanently to assume ; as in the case of 

 Birds and Reptiles, which do not come forth from the investments of 

 the egg, until they have attained the form characteristic of the group 

 to which they belong. Or it may only serve for the early part of the 

 process ; and one of two methods may then be employed to complete 

 it; either a new connexion is formed between the parent and the 

 embryo, by which the former continues to supply the latter with nutri- 

 ment, more directly from its blood, as is the case with Mammalia, or 

 the embryo issues from the egg, in a condition very unlike that which 

 it is permanently to attain, but in a form which enables it to acquire its 

 own nourishment, and to pass through the latter stages of its evolution 

 quite independently of any assistance from its parent : this is the case 

 with a large proportion of the Invertebrata. 



792. The Ova, like the seminal cells, are scattered through the soft 

 parenchyma of the body, in animals of the lowest class ; but they are 



