Fig. 136.

cavity; whence it passes out by openings that lead directly to the exterior. The Testis in Man is formed, in every essential particular, upon the plan of the ordinary Glands. It consists of several distinct lobules, separated by processes of the fibrous envelope, or tunica albuginea, which pass down between them; and each lobule consists of a mass of convoluted tubuli seminiferi, through which blood-vessels are minutely distributed. The diameter of these tubuli is tolerably uniform; being, when they are not over-distended, from 1-195th to 1-170th of an inch. They form frequent anastomoses with each other; and on this account it is difficult to trace out their free or cæcal extremities. The tubuli of each testis discharge their contents into an efferent duct, the Vas deferens; and by this the product is conveyed into the Vesiculi seminalis on each side, which, like the gall-bladder and urinary bladder, serves to store up the secretion until the proper time arrives for discharging it. The product of the action of the Testis consists of a fluid, through which the Spermatozoa are diffused; these last bodies being usually set free by the rupture of the seminal cells, before they leave the tubuli of the testis. It is difficult to determine the precise characters of the fluid portion 1. of the secretion; as this is mingled with other se- 3. 3. The lobuli testis. 4, 4. cretions (such as that of the Prostate gland, and of testis. 6. The vasa efferentia, the mucous lining of the Vesiculæ seminales and of which six only are represpermatic ducts), before it is emitted. And an The coni vasculosi, constituexact analysis is not of much consequence; since epididymus. 8. The body of there can be no doubt that the peculiar powers of minor of the epididymus. 10. the fluid depend upon the Spermatozoa. It may vasculum aberrans. be stated, however, that the Spermatic fluid has an alkaline reaction, and that it contains albumen, together with a peculiar animal principle termed Spermatine; and that it also includes saline matter, consisting chiefly of the muriates and phosphates, especially the latter, which form crystals when the fluid has stood for some little time.

1.

The tunica albuginea.

2, 2. The mediastinum testis.

The vasa recta. 5. The rete

sented in this diagram. 7.

ting the globus major of the

the epididymus. 9. The globus The vas deferens. 11. The

787. The Spermatozoa, or minute filamentous bodies set free by the rupture of the spermatic cells, are distinguished by their power of spontaneous movement, which occasioned them to be long regarded as proper Animalcules. It is now clear, however, from the history of their development, as well as from other considerations, that they cannot be justly regarded in this light; and that they are analogous to the reproductive particles of Plants, which, in many cases, exhibit a spontaneous motion of extraordinary activity, after they have been set free from the parent structure. The Human Spermatozoa consists of a little oval flattened "body," from the 1-600th to the 1-800th of a line in length; from which proceeds a filiform "tail," gradually tapering to a very fine point, of 1-50th or at most 1-40th of a line in length. The whole is perfectly transparent; and nothing that can be called structure can be

satisfactorily distinguished within it. The movements are principally excited by the undulations of the tail, which give a propulsive action to the body. They may continue for many hours after the emission of the fluid; and they are not checked by its admixture with other secretions, such as the urine, and the prostatic fluid. When the seminal fluid remains in contact with a living surface (as when deposited in the generative organs of the female), the Spermatozoa may retain their vitality for some days; and an instance has already been referred to (§ 240), in which the later stages of the development of the Spermatozoa actually take place in this situation,-the seminal fluid emitted by the male (among many Crustacea) not containing any Spermatozoa completely formed, but numerous spermatic cells, which undergo the remainder of their development, and then rupture and set free their contents, within the oviducts of the female.

788. The power of procreation does not exist in the Human Male (except in rare cases) until the age of from 14 to 16 years; at which epoch, the sexual organs undergo a much-increased development; and the instinctive desire, which leads to the use of them, is awakened in the mind. From that time to an advanced age, the procreative power remains, in the healthy state of the system; unless it be exhausted by excessive use of it, or by too energetic a direction of the mental or corporeal powers to some other object. The formation of Seminal fluid being, like the proper acts of Secretion, very much influenced by conditions of the Nervous System, is increased by the continual direction of the mind towards objects which arouse the sexual propensity; and thus, if sexual intercourse be very frequent, a much larger quantity of the fluid will be produced than if it is more rarely emitted, although the amount discharged on each occasion will be less. The formation of this product is evidently a great tax upon the corporeal powers; and it is a well-known fact, that the highest degree of bodily and mental vigor is inconsistent with more than a very moderate indulgence in sexual intercourse; whilst nothing is more certain to reduce the powers, both of body and mind, than excess in this respect.

789. It may be stated as a general law, prevailing equally in the Vegetable and Animal kingdoms,—that the development of the individual, and the reproduction of the species, stand in an inverse ratio to each other. We have seen that, in many organized beings, the death of the parent is necessary to the production of a new generation; and even in numerous species of Insects it follows very speedily upon the sexual intercourse. It is a curious fact, that Insects which usually die, the male almost immediately after the act of copulation, and the female very soon after the deposition of the eggs, may be kept alive for many weeks or even months, by simply preventing the copulation. And there can be no doubt that, in the Human race, early death is by no means an unfrequent result of the excessive or premature employment of the genital organs; and where this does not produce an immediately-fatal result, it lays the foundation of future debility, that contributes to produce any forms of disease to which there may be a constitutional predisposition, especially those of a Scrofulous nature.

790. The emission of the Spermatic fluid is an act of a purely reflex

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 ganglionic centre of the circle of afferent and efferent nerves connected with this organ), a reflex contraction of the muscles surrounding the Vesiculæ 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 Compressor 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 contraction 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 materials 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 peculiar 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 temperature) 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 nutriment, 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

more commonly developed in certain distinct portions of the fabric; being sometimes formed in the midst of solid masses of areolar or cellular texture; whilst in other instances they are developed, like the spermatic cells, in the interior of tubes and vesicles resembling those of glands, and furnished with an excretory duct. The latter condition obtains in the greater proportion of the higher Invertebrated animals, and in some Fishes; but in the Vertebrated classes we return to the type which characterizes the egg-producing organs in many Zoophytes, -namely, the development of the egg in the midst of a mass of solid parenchyma, from which it gradually makes it way, to escape into the visceral cavity. The Ovarium of the Mammal, Bird, or Reptile, as well as that of most Fishes, differs entirely, therefore, from that of the Invertebrata; for the latter have all the essential characters of true glands; whilst the former are nothing else than masses of parenchyma, copiously supplied with blood-vessels, and having dispersed through their substance certain peculiar cells, termed ovisacs, within which the ova are developed. In order that the latter may be set free, not only must the ovisac itself burst (like parent-cells in general), but the peculiar tissue and the envelopes of the ovarium must likewise give way. When the ova thus escape into the abdominal cavity, they may lie there for some time, at last to be discharged through simple openings in its walls, as happens in those Fishes which have this form of ovarium: or they may be at once received into the trumpet-shaped expansion of tubes, that shall convey them to these orifices. These tubes are termed oviducts, in common with the excretory ducts of the glandular ovaria of Invertebrated animals; for their function is the same,-that of conveying the ova to the outlet by which they are extruded from the body.

The Uterus with its appendages viewed on their anterior aspect. 1. The body of the uterus. 2. Its fundus 3. Its cervix. 4. The os uteri. 5. The vagina; the number is placed on the posterior raphe or columns, from which the transverse rugæ are seen passing off at each side. 6, 6. The broad ligament of the uterus. 7. A convexity of the broad ligament formed by the ovary. 8, 8. The round ligaments of the uterus. 2,9 The Fallopian tubes. 10, 10. The fimbriated extremities of the Fallopian tubes; on the left side the mouth of the tube is turned forwards in order to show its ostium abdominale. 11. The ovary. 12. The utero-orarian ligament. 13. The Fallopio-ovarian ligament, upon which some small fimbriae are continued for a short distance. 14. The peritoneum of the anterior surface of the uterus. This membrane is removed on the left side, but on the right is continuous with the anterior layer of the broad ligament.

They are represented in Mammalia by the Fallopian tubes, which are true oviducts, although they terminate in the uterus instead of proceeding directly to the outlet. And it is by the fimbriated extremities of the Fallopian tubes (Fig. 137, 10, 10), which apply themselves closely

to the surface of the ovaries at the time of the discharge of the ova, that these are received and conveyed to the uterus, instead of being allowed (as in some of the lower animals) to fall into the abdominal cavity.

793. There are many cases among the lower classes, in which the ovum is retained within the oviducts, so that the young comes into the world alive; and there are few in which, during this delay, it receives a direct supply of additional nourishment from the fluids of its parent. It is in the Mammalia, however, that we find the most remarkable and complete provision for this purpose. Still, the lowest division of this group approximates closely, in the type of its generative apparatus to the Oviparous Vertebrata; for the oviducts of the Monotremata remain distinct from each other, and terminate separately, in the uro-genital canal, each of them having first undergone dilatation into a uterine cavity, so that these animals have two completely distinct uteri. In the Marsupialia, there is a closer approximation of the two lateral sets of organs on the median line; for the oviducts converge towards one another, and meet on the median line, but without coalescing; so that these animals have a true "double uterus," opening by two orifices into the vaginal canal,—a condition which is sometimes met with as a malformation in the Human female. The vaginal canal, however, is also double; which is less frequently observed in the Human species. The two preceding orders constitute the sub-class of Implacental Mammals; the development of their ova within the uteri being cut short at a period anterior to the formation of the placenta (§ 818).-As we ascend through the series of Placental Mammals, we find the lateral coalescence of the uterine dilatations of the Fallopian tubes becoming more and more complete. It first shows itself in the vagina, which is everywhere single, although a trace of separation into two lateral halves is seen in the Mare, Ass, Cow, Pig, and Sloth, in which animals it is traversed, in the virgin state, by a narrow, vertical partition. In many of the Rodentia, the uterus still remains completely divided into two lateral halves, opening into the vagina by separate orifices; whilst in others, these coalesce at their lower portion, forming a rudiment of the true "body" of the uterus of the Human female. This part increases in the more elevated Herbivora and Carnivora, at the expense of the lateral ununited portions, which are now termed the "cornua;" but even in the lower Quadrumana, the uterus is somewhat cleft at its summit, and the "angles," into which the oviducts enter, form a considerable part of the whole organ. As we ascend through the Quadrumanous series towards Man, we find the "body" of the uterus increasing, and the "angles" diminishing in proportion, until the original division is completely lost sight of, except in the slight dilatation of the cavity at the points at which the Fallopian tubes enter it.

794. Having thus briefly noticed the most important characters of the organs provided for the original production and for the subsequent reception of the ova, we have now to inquire into the history of their development. The essential structure of the ovule, or unfertilized egg, appears to be the same in all animals. It consists externally of a membranous sac, so termed, from the nature of its contents, the vitelline