Vegetable Husbands.--Within the cup formed by the calyx and corolla are placed the _stamens_ and _pistils_ of the flower, the first being the male organs proper, and the second the female organs of the flower.

The stamen is composed of a stem or filament, at the summit of which are placed two little sacks called the _anther_, which contain a fine, microscopic dust, the _pollen_, which contains the male reproductive element of the flower. This part of the plant corresponds to the male organ of reproduction in animals. A stamen has been called, not inaptly, a vegetable husband. Some flowers have many stamens, or vegetable husbands, which reminds us of the custom in Thibet and some other Eastern countries which allows a woman to have several husbands.

Polygamous Flowers.--The great naturalist, Linnaeus, whose name was immortalized by his careful study and cla.s.sification of organized life, made the number of stamens possessed by various flowers the basis of a systematic cla.s.sification.

For example, a flower having but one stamen was cla.s.sed as _monandria_, which means, literally, one husband; one having two stamens was cla.s.sified as _diandria_; flowers having a large number of male organs were termed _polyandria_, or many husbands.

The Female Organ of Flowers.--The _pistil_ occupies the very center of the flower. It produces and contains in a cell, the female element, termed the _ovule_. It is surmounted by the _style_ and the _stigma_.

A series of plants in which the s.e.xual organs are not visible to the eye are termed _cryptogamia_, which means literally, hidden marriages.

As we proceed to study the anatomy of the human s.e.xual apparatus we shall be constantly struck with the remarkable correspondence between animals and vegetables in the structure and functions of the s.e.xual apparatus.

s.e.xual Organs of Animals.--The male reproductive element is called a _spermatozoon_ or _zoosperm_. The female element is called an _ovum_, literally, an egg.

The Spermatozoon.--The male reproductive element of animals is formed by an organ called the _testis_, or _t.e.s.t.i.c.l.e_, of which each male possesses two. They are elastic, glandular bodies, and are formed within the cavity of the abdomen, near the kidneys, but usually pa.s.s out of the abdominal cavity and descend to their permanent position before birth. The opening in the abdominal wall is usually completely closed in a short time; but occasionally it remains open, giving rise to congenital hernia, an accident in which a loop of intestine follows the t.e.s.t.i.c.l.e down into the s.c.r.o.t.u.m, either completely or partially.

In a few animals, as in the porcupine, the opening is never fully closed, and the testis remains in the cavity of the body most of the time, pa.s.sing out only at certain periods. We also occasionally meet cases of human beings in which the testes have never descended from their place in the abdominal cavity, giving the individuals the appearance of eunuchs. This condition, however, though an abnormal one, does not in any way interfere with the function of the organs, as those who happen to possess it often imagine. We have also met with cases in which the organs were movable, and could readily be pressed up into the abdominal cavity, through the unclosed inguinal cavity, which afforded them a pa.s.sage downward in the process of development.

As before remarked, these peculiarities do not affect the functions of the organs in any appreciable degree, although they not infrequently give rise to some apprehension on the part of those subject to them.

The left t.e.s.t.i.c.l.e is sometimes a little smaller than the right, another fact which is seized upon by quacks as a means of exciting the fears of young men who have been addicted to bad habits, although the peculiarity is generally without important significance.

The t.e.s.t.i.c.l.es are connected with the urinary pa.s.sage by means of two ducts which terminate near the base of the bladder, at which point they connect with the urethra. We need not dwell at further length upon the structure of the t.e.s.t.i.c.l.es, as this subject receives fuller attention elsewhere.

Human spermatozoa are about 1/600 of an inch in length. Those of reptiles are very much larger. One of the remarkable features of these minute elements is their peculiar movements. While alive, the filamentous tail is in constant action in a manner strongly resembling the movements of the caudal appendage of a tadpole. This wonderful property led the earlier observers to believe that they were true animalcula. But they are not to be regarded as such, though one can scarcely make himself believe otherwise while watching their lively evolutions, and apparent volitionary movement from one point to another.

Spermatozoa originate in the testis as cells, which are filled with granules. After a time, each granule acquires a long appendage, and then the cell has become converted into a bundle of small zoosperms.

Development still continues, until finally the thin pellicle on the outside of the bundle is ruptured, thus liberating the young spermatozoa, which speedily complete their full development. The spermatozoon is pure protoplasm, which is the basis of all life, and its power of spontaneous motion is due to this fact.

In man, the formation of spermatozoa continues with greater or less rapidity from p.u.b.erty to old age, though at the two extremes of existence they are imperfectly developed. When not discharged from the body, they are said to be absorbed. Some physiologists claim that they are composed of a substance identical with nerve tissue, and that by absorption they play a very important part in the development and maintenance of the nervous system.

It is a.s.serted by good authorities that the reproductive element in man is not so well developed as to be really fit for the reproduction of the species before the age of twenty-four or twenty-five. After the age of forty-five or fifty, the reproductive elements deteriorate in quality, and become again unfitted for vigorous procreation.

The fully developed zoosperms are suspended in a transparent, gelatinous fluid, which, mingled with the secretion of the prostate gland and other fluids which it meets during its expulsion from the body, const.i.tutes the _s.e.m.e.n_.

The Ovum.--The female element of generation, the ovum, is produced by an organ called the _ovary_, of which there are two in each individual.

In size and form, the ovary closely resembles the t.e.s.t.i.c.l.e. Like the latter organ, also, it is formed within the body early in the process of development; but instead of pa.s.sing outward and downward, as does the t.e.s.t.i.c.l.e, it remains within the abdominal cavity, suspended in place by ligaments. It is connected with a duct which receives the ovum as it is discharged, and conveys it to the uterus.

The human ovum varies in size from 1/240 to 1/120 of an inch in diameter, and consists of a single cell. Ova are not formed in such large numbers as zoosperms. As a general rule, in the human female, a single ovum is developed and discharged once in about four weeks, during the period of s.e.xual activity.

Fecundation.--It is often asked, and the question has elicited some discussion, Which is the princ.i.p.al reproductive element; the zoosperm, or the ovum? The ancients supposed the male element to be the essential element, being simply nourished and developed by the female; but modern research in biological science does not sustain this view. Probably neither one enjoys especial preeminence; for neither can undergo complete development without the other. In very rare cases, the ovum has been observed to undergo a certain amount of development of itself; but a perfect individual can be produced only by the union of the two kinds of elements, which process is known as _fecundation_. The instant this union occurs, the life of a new individual begins. All the changes which result between that moment and the birth of the individual are those of development only. Indeed, the same existence continues from the instant of the union of the two elements, not only until birth, but through growth, the attainment of maturity, the decline of life, and even until death.

It is interesting to observe the different methods by which fecundation is effected, both in plants and animals, for this is a process common to both.

Fecundation in Flowers.--The great naturalist, Linnaeus, was the first to explain the reproductive process in plants. He tells us that "the flower forms the theater of their amours; the calyx is to be considered as the nuptial bed; the corolla const.i.tutes the curtains; the anthers are the testes; the pollen, the fecundating fluid; the stigma of the pistil, the external genital aperture; the style, the v.a.g.i.n.a, or the conductor of the prolific seed; the ovary of the plant, the womb; the reciprocal action of the stamens on the pistil, the accessory process of fecundation."

Thus marvelous is the a.n.a.logy between the reproductive organs and their functions in plants and animals. Through this one vital process we may trace a close relation between all the forms of life, from the humblest plant, or even the mere specks of life which form the green sc.u.m upon a stagnant pool, to man, the masterpiece of creation, the highest of all animated creatures. In all the realm of Nature there can be found no more remarkable evidences of the infinite skill and wisdom of the Creator of all things.

In many instances the action of plants seems almost to be prompted by intelligence. At the proper moment, the corolla contracts in such a way as to bring the stamens nearer to the stigma, or in contact with it, so as to insure fecundation. In some aquatic plants the flowers elevate themselves above the surface of water while the process of fecundation is effected; submerging themselves again immediately afterward.

Other very curious changes occur in flowers of different species during the reproductive act. The stigma is observed to become moistened, and even to become distinctly odorous. Often, too, it becomes intensely congested with the juices of the plant, and sometimes even acquires an uncommon and most remarkable degree of contractility. This is the case with the stigma of the tulip and one variety of sensitive plant, and is in these plants observed to occur not only after the application of the pollen to the stigma, but when excited by any other means of stimulation. The flowers of some plants, during and after fecundation, also show an increase of heat, in some cases so marked as to be readily detected with the thermometer. This is said to be the case with the _arum_ of Italy.

In some plants in which the pistil is longer than the stamens, thus elevating the stigma above the anthers, the female organ is often observed to bend over and depress itself so as to come within reach of the anthers.

In most instances the fecundation of flowers is chiefly effected through a purely mechanical process, though in these cases also we see a wonderful adaptation of parts to conditions.

When the male and female parts of flowers are situated on different plants, as is the case in the willow, the poplar, the melon vine, and many other species, the pollen of the male flower is wafted by the wind or gentle breeze to the stigma of the female flower, which will usually be found at no very great distance, although fertilization may take place in this way at very considerable distances. Bees, moths, and many other species of insects, serve a very important purpose in this work, transporting the fertilizing dust upon their wings, antennae, sucking-tubes, and feet. Small birds, and even the humble snail, which would scarcely be credited with any useful function, are also very serviceable in the same direction. The part performed by insects in the reproductive process of many plants is so great that they have been very poetically termed "the marriage priests of flowers."

Nature provides for thorough fecundation in these cases by placing the plants which bear the male and the female flowers near each other. This fact accounts for the unproductiveness of certain varieties of strawberries unless mixed with plants of some other variety, it being well known to nursery-men that some varieties produce only the female parts of flowers.

Modes of Fecundation in Animals.--The modes by which fecundation is effected in animals are still more various and wonderful than in plants.

In some of the lower animals, as in most fish and reptiles, both elements are discharged from the bodies of the parents before coming in contact, there being no contact of the two individuals. In this cla.s.s of animals the process is almost wholly a.n.a.logous to fecundation in those plants in which the male and female flowers are on different plants or different parts of the same plant. In the female fish, a large number of ova are developed at a certain season of the year known as the sp.a.w.ning season. Sometimes the number reaches many thousands. At the same time, the t.e.s.t.i.c.l.es of the male fish, which are contained within the abdominal cavity, become distended with developed zoosperms. When the female seeks a place to deposit her eggs, the male closely follows; and as she drops them upon the gravelly bottom, he discharges upon them the zoosperms by which they are fecundated. The process is a.n.a.logous to some species of frogs. When the female is about to deposit her eggs, the male mounts upon her back and rides about until the eggs are all deposited, discharging upon them the fertilizing spermatozoa as they are laid by the female.

In higher orders of animals, fecundation takes place within the generative organs of the female by contact between the male and the female organs. To effect this, there are necessitated certain accessory organs, the _p.e.n.i.s_ in the male and the _v.a.g.i.n.a_ in the female.

Nothing in all the range of nature is more remarkable than the adaptation of the two varieties of s.e.xual organs in each species. This necessary provision is both a powerful means of securing the perpetuation of the species, and an almost impa.s.sable barrier against amalgamation.

The act of union, or s.e.xual congress, is called _coitus_ or _copulation_.

It is accompanied by a peculiar nervous spasm due to excitement of special nerves princ.i.p.ally located in the _p.e.n.i.s_ in the male, and in an extremely sensitive organ, the _c.l.i.toris_, in the female. The nervous action referred to is more exhausting to the system than any other to which it is subject.

Union of the Ovum and Zoosperm.--The zoosperms not only come in contact with the ovum, but penetrate the thin membrane which incloses its contents, and enter its interior, where they disappear, becoming united with its substance. In the ova of certain fishes, small openings have been observed through which the spermatozoa find entrance. Whether such openings exist in human ova is an undecided question; but it is probable that they do.

Curious Modes of Reproduction.--A peculiar kind of reproduction is observed in a variety of polyp, a curious animal which very much resembles a shrub in appearance. It attaches itself to some solid object, and then, as it grows, sends out little protuberances resembling buds.

Some of these separate and fall off, swimming about as separate animals.

These never become like the parent polyp; but they lay eggs, which hatch, and become stationary polyps like their grandparent, and in their turn throw off buds to form swimming polyps. In this case we have two kinds of generation combined, alternating with each other.

Plant-lice afford a curious ill.u.s.tration of a similar generation. Males and females unite and produce eggs. The creatures produced by the hatching of eggs are neither males nor perfect females. They are _imperfect females_. They are all alike, so that no s.e.xual union occurs.

Instead of laying eggs, they produce live young like themselves, which appear to be developed from internal buds similar to the external buds of the polyp. After this method of reproduction has continued for eight or ten generations, a few perfect individuals appear, and the first process is repeated.

The common honey-bee affords another ill.u.s.tration like the last. A virgin queen sometimes lays eggs, which always produce males, or drones.

After union with a male, she lays eggs in the royal cells which become perfect females like herself. She also seems to have the power to lay, at will, unfecundated eggs, from which drones are produced.

Human Beings Are Developed Buds.--It has been very aptly suggested by an eminent physiologist that the ovum and zoosperm may be correctly considered as internal buds. Thus it would appear that generation is universally a process of budding. A child is but a compound bud, an offshoot from its parents. This idea is not a mere fancy, but has a scientific basis. As all the exquisite details of the most beautiful flower are in essence contained within the tiny bud which first makes its appearance, so is the developed human being, the full-grown man or woman, virtually contained within the tiny cell called the ovum after it has been impregnated or fecundated by the zoosperms. In short, men and women are blossoms in a strictly scientific sense.

Fecundation in Hermaphrodites.--The process of fecundation in hermaphrodite animals is very peculiar. In some cases, as in the snail, the union of two individuals is usually necessary, though each possesses both kinds of organs. In other cases, as in the tape-worm, the oyster, and numerous other mollusks, a single individual has the power to fertilize its own ova, thus being wholly independent. Human hermaphrodites are usually so deformed that fecundation is not effected, which is a fortunate safeguard against the multiplication of such monstrosities.

Development.--After the union of the two elements, known as fecundation or _conception_, if the conditions are favorable, development occurs, and the little germ is in due process of time developed into an individual which is an exact counterpart of its parents. During this developmental process, the embryonic being is variously treated by different cla.s.ses of animals.

Unprotected Development.--Most fishes and reptiles discharge their ova before fecundation, or soon after, and pay no further attention to them.

The fish deposits its eggs in a little hollow scooped out in the gravelly bed of a stream, or sows them broadcast upon the waters. The turtle buries its eggs in the sand, and leaves them to be hatched by the sun.

The ostrich disposes of her eggs in the same way. Many other species of animals pay no regard to the protection of the germs which are destined, if placed under favorable conditions, to become individuals like themselves.

Partial Protection of the Ovum.--There are some exceptions, however, to this general rule among fishes and reptiles. Even fishes manifest a degree of parental solicitude in certain cases. The male of a species of South American fish gathers up the eggs after fecundation has taken place, and carries them in his mouth until they are hatched. Another male fish carries the eggs of his mate in a little pouch upon the lower and posterior part of his body.

Certain species of frogs carry their eggs wound about their legs; others suspend them from the abdomen. Another variety carries its young upon its back. Prof. Wyman describes a "swamp toad" which patiently takes the eggs of his mate, one by one, and fastens them upon her back, observing great regularity in arrangement. These several devices are evidently for the purpose of protecting, in some degree, the young individual during the helpless stage of its existence.

Development in the Higher Animals and Man.--Higher animals are less prolific, and their development is a more complicated process; hence, their young need greater protection, and, for this reason, the ova, instead of being discharged from the body of the female after fecundation, are retained.[3] As we have seen that a suitable receptacle is sometimes provided outside of the body, so now a receptacle is needed, and is provided in the interior of the body of the female. This receptacle is called

[Footnote 3: Curious examples of internal development sometimes occur in animals which usually deposit eggs. Snakes have been known to produce both eggs and living young at the same time. At the annual meeting of the American Society for the Advancement of Science, at Detroit, Mich., in August, 1875, we had the pleasure of examining a specimen, exhibited by Prof. Wilder, of a chick which had undergone a considerable degree of development within the ovary of the hen. It had a head, a rudimentary brain, and internal viscera, but no feathers nor limbs. It was, in fact, an egg hatched before it had been laid. The anomaly excited much interest at that time and since among biologists.]