The Uterus.--This is a hollow, pear-shaped organ, located in the median line, just behind the bladder, between it and the r.e.c.t.u.m. It is supported in place by various ligaments and by the juxtaposition of other organs. Its larger end is directed upward, and communicates upon each side with a very narrow tube which is prolonged outward on either side until it nearly touches the ovary of the same side. Its lower and smaller end fills the internal extremity of the pa.s.sage previously described as the v.a.g.i.n.a. When an ovum is matured, it escapes from the ovary into the narrow tube referred to, called the _Fallopian tube_, and pa.s.ses down into the cavity of the uterus. If fecundation does not occur, it is expelled or absorbed after six to twelve or fourteen days.

If copulation occurs, however, zoosperms are brought into the cavity of the uterus, and, coming in contact with the ovum, fecundate it. This is _conception_. When the natural process is allowed to proceed, development occurs.

Uterine Gestation.--This is the term applied to the process last referred to. We shall not attempt to describe in detail this most wonderful and intricate of all living processes; but will sketch only the chief points, leaving the reader who would obtain a more complete knowledge of the subject to consult any one of the numerous physiological and obstetrical works which deal with it in a very exhaustive manner.

As soon as the ovum is impregnated by the male element, it begins a process of symmetrical division. The first division produces two cells out of the single one which first existed. By the next division, four segments are produced; then eight, sixteen, etc. While this process is going on, the ovum becomes adherent to the internal wall of the uterus, and is soon enveloped by its mucous membrane, which grows up about and incloses it.

The Primitive Trace.--When the process of segmentation has advanced to a certain point, the cells are aggregated together in a compact layer at the surface. Soon a straight line appears upon this layer, which is called the _primitive trace_. This delicate line becomes the basis for the spinal column; and upon and about it the whole individual is developed by an intricate process of folding, dividing, and reduplication of the layer of cells. One end of the line becomes the head, and the other becomes the tail. Even man has a caudal appendage at an early stage of his existence. After a further lapse of time, little excrescences, buds, or "pads," appear in the proper positions to represent the arms and legs. After further development the ends split up into fingers and toes, and by the continued development of the parts, perfect arms and legs are formed.

Curious Relation to Lower Animals.--It is a very remarkable fact that in the lower animals we have numerous examples in which the permanent condition of the individual is the same as some one of the stages through which man pa.s.ses in the process of development. The same author previously quoted makes the following interesting statements:--

"The webbed feet of the seal and ornithorhynchus typify the period when the hands and feet of the human embryo are as yet only partly subdivided into fingers and toes. Indeed, it is not uncommon for the 'web' to persist to some extent between the toes of adults; and occasionally children are born with two or more fingers or toes united to their tips.

"With the seal and the walrus, the limbs are protruded but little beyond the wrist and ankle. With the ordinary quadrupeds, the knee and elbow are visible. The cats, the lemurs, and the monkeys form a series in which the limbs are successively freed from the trunk, and in the highest apes they are capable of nearly the same movements as the human arm and leg, which, in their development, pa.s.sed through all these stages."

Simplicity of Early Structures.--The first structures formed are exceedingly simple in form. It is only by slow degrees that the great complicity which characterizes many organs is finally attained. For example, the heart is at first only a straight tube. By enlargement and the formation of longitudinal and transverse part.i.tions, the fully developed organ is finally produced. The stomach and intestines are also at first but a simple straight tube. The stomach and large intestine are formed by dilatation; and by a growth of the tube in length while the ends are confined, the small intestines are formed. The other internal organs are successively developed by similar processes.

The Stages of Growth.--At first insignificant in size--a simple cell, the embryonic human being steadily increases in size, gradually approximating more and more closely to the human form, until, at the end of about nine calendar months or ten lunar months, the new individual is prepared to enter the world and begin a more independent course of life. The following condensation of a summary quoted by Dr.

Austin Flint, Jr., will give an idea of the size of the developing being at different periods, and the rate of progress:--

At the end of the third week, the embryon is a little less than one-fourth of an inch in length.

At the end of the seventh week, it is three-fourths of an inch long.

The liver, lungs, and other internal organs are partially formed.

At the eighth week, it is about one inch in length. It begins to look some like a human being, but it is impossible to determine the s.e.x.

At the third month, the embryon has attained the length of two to two and one-half inches. Its weight is about one ounce.

At the end of the fourth month, the embryon is called a fetus. It is from four to five inches long, and weighs five ounces.

At the fifth month, the fetus is nearly a foot long, and weighs about half a pound.

At the sixth month, the average length of the fetus is about thirteen inches, and its weight one and a half to two pounds. If born, life could continue a few minutes.

At the seventh month, the fetus is from fourteen to fifteen inches long, and weighs two to three pounds. It is now viable (may live if born).

At the eighth month, the length of the fetus is from fifteen to sixteen inches, and its weight from three to four pounds.

At the ninth month, the fetus is about seventeen inches long, and weighs from five to six pounds.

At birth, the infant weighs a little more than seven pounds, the usual range being from four to ten pounds, though these limits are sometimes exceeded.

Duration of Gestation.--The length of time required for the development of a human being is usually reckoned as about forty weeks. A more precise statement places it at about two hundred and seventy-eight days. This limit is often varied from. Cases have occurred in which a much longer time has been required, and numberless cases have occurred in which human beings have been born several weeks before the expiration of the usual time, as stated. There is some uncertainty respecting the exact length of the period of gestation, which grows out of the difficulty of determining, in many cases, the exact time when conception takes place.

Uterine Life.--The uterine life of the new individual begins with the impregnation of the ovum, which occurs the instant it is brought in contact with the zoosperms of the male. While in the uterus, the young life is supported wholly by the mother. She is obliged to provide not only for her own sustenance, but for the maintenance of her child. And she must not only eat for it, but breathe for it as well, since it requires a constant and adequate supply of oxygen before birth as much as afterward.

How the Unborn Infant Breathes.--Oxygen and nutriment are both supplied to it through the medium of an organ called the _placenta_, which is a spongy growth composed almost entirely of blood-vessels, and is developed upon the inner wall of the uterus, at the point at which the ovum attaches itself after fecundation. The growing fetus is connected with this vascular organ by means of a sort of cable, called the _umbilical cord_. The cord is almost entirely composed of blood-vessels which convey the blood of the fetus to the placenta and return it again.

The fetal blood does not mix with that of the mother, but receives oxygen and nourishment from it by absorption through the thin walls which alone separate it from the mother's blood.

The umbilical cord contains no nerves, as there is no nervous connection between the mother and the child. The only way in which the child can be influenced by the mother is through the medium of the blood, to changes in which it is very susceptible, as we shall see more clearly hereafter.

The cord is attached to the body of the child at the point called the _navel_, being cut off at birth by the _accoucheur_. With the placenta, it is expelled soon after the birth of the child, and const.i.tutes the shapeless ma.s.s familiarly known as the _after-birth_, by the retention of which the most serious trouble is occasionally caused.

Parturition.--At the end of the period of development, the young being is forcibly expelled from the laboratory of nature in which it has been formed. In other words, it is born; and this process is termed _parturition_. Though, at first thought, such an act would seem an utter impossibility, yet it is a very admirable ill.u.s.tration of nature's adaptation of means to ends. During the months of gestation, while the uterus has been enlarging to accommodate its daily increasing contents, the generative pa.s.sages have also been increasing in size and becoming soft and distensible, so that a seeming impossibility is in due time accomplished without physical damage, though possibly not without intense suffering. However, it is a most gratifying fact that modern medical science may do much to mitigate the pains of childbirth. It is possible, by a proper course of preparation for the expected event, to greatly lessen the suffering usually undergone; and some ladies a.s.sert that they have thus avoided real pain altogether. Although the curse p.r.o.nounced upon the feminine part of the race, in consequence of the sin of Eve, implies suffering in the parturient act, yet there is no doubt that the greater share of the daughters of Eve are, through the perverting and degenerating influences of wrong habits and especially of modern civilization, compelled to suffer many times more than their maternal ancestor. We have sufficient evidence of this in the fact that among barbarian women, who are generally less perverted physically than civilized women, childbirth is regarded with very little apprehension, since it occasions little pain or inconvenience.

The same is true of many women among the lower laboring cla.s.ses. In short, while it is true that more or less suffering must always accompany the parturient act, yet the excessive pain usually attendant upon the process is the result of causes which can in many cases be removed by proper management beforehand and at the time of confinement.

After being relieved of its contents, the uterus and other organs rapidly return to nearly their original size.

Changes in the Child at Birth.--In the system of the child a wonderful change occurs at the moment of its expulsion into the outer world. For the first time, its lungs are filled with air. For the first time they receive the full tide of blood. The whole course of the circulation is changed, and an entirely new process begins. It is surprising in how short a s.p.a.ce of time changes so marvelous can be wrought.

Nursing.--The process of development is not fully complete at birth.

The young life is not yet prepared to support itself; hence, still further provision is necessary for it. It requires prepared food suited to its condition. This is provided by the _mammae_, or b.r.e.a.s.t.s, of the female, which are glands for secreting milk. The fully developed gland is peculiar to the female; but a few instances have been known in which it has been sufficiently developed to become functionally active in men, as well as in young girls, though it is usually inactive even in women until near the close of gestation. It is a curious fact that the b.r.e.a.s.t.s of a new-born child occasionally contain milk.

The first product of the mammae is not the proper milk secretion, but is a yellowish fluid called _colostrum _. The true milk secretion begins two or three days after delivery.

The lacteal secretion is influenced in a very remarkable manner by the mental conditions of the mother. By sudden emotions of grief or anger, it has been known to undergo such changes as to produce in the child a fit of indigestion, vomiting, diarrhea, and even convulsions and death. Any medicine taken by the mother finds its way into the milk, and often affects the delicate system of the infant more than herself.

This fact should be a warning to those nursing mothers who use stimulants. Cases are not uncommon in which delicate infants are kept in a state of intoxication for weeks by the use of alcoholic drinks by the mother. The popular notion that lager-beer, ale, wine, or alcohol in any other form, is in any degree necessary or beneficial to a nursing woman is a great error which cannot be too often noticed and condemned.

Not only is the mother injured, instead of being benefited by such a practice, but great injury, sometimes life-long in its consequences, is inflicted upon the babe at her breast who takes the intoxicating poison at second hand, and is influenced in a fourfold degree from its feebleness and great susceptibility.

ANATOMY OF THE REPRODUCTIVE ORGANS.

Having now considered the functions and somewhat of the structures of the princ.i.p.al organs of reproduction, we may obtain a more definite idea of the relation of the several organs of each cla.s.s by a connected review of the anatomy of the parts.

Male Organs.--As previously stated, the external organs of generation in the male are the _p.e.n.i.s_ and the _t.e.s.t.i.c.l.es_, the latter being contained in a pouch called the _s.c.r.o.t.u.m_. The p.e.n.i.s is the organ of urination as well as copulation. Its structure is cellular, and it contains a vast number of minute coils of blood-vessels which become turgid with blood under the influence of s.e.xual excitement, producing distention and erection of the organ. A ca.n.a.l pa.s.ses through its entire length, called the _urethra_, which conveys both the urine and the seminal fluid. The organ is protected by a loose covering of integument which folds over the end. This fold is called the _foreskin_ or _prepuce_.

The fluid formed by each t.e.s.t.i.c.l.e is conveyed by the _vas deferens_, a curved tube about two feet in length, to the base of the bladder.

Here the vas deferens joins with another duct which communicates with an elongated pouch, the _vesicula seminalis_, which lies close upon the under side of the bladder. The single tube thus formed, the _ejaculatory duct_, conveys the seminal fluid to the urethra, from which it is discharged.

As the production of seminal fluid is more or less constant in man and some animals, while its discharge is intermittent, the vesiculae seminales serve as reservoirs for the fluid, preserving it until required, or allowing it to undergo absorption. Some claim that the zoosperms are matured in these organs. They always contain seminal fluid after the age of p.u.b.erty. During coition, their contents are forcibly expelled by a spasmodic contraction of the muscles which surround them and the ducts leading from them.

The Prostate Gland.--Surrounding the ejaculatory ducts and their openings into the urethra at the base of the bladder is the _prostate gland_, which produces a peculiar secretion which forms a considerable portion of the seminal fluid, being mingled with the secretion of the testes during its e.j.a.c.u.l.a.t.i.o.n. This gland sometimes becomes the seat of somewhat serious disease. In old age it usually becomes somewhat indurated, and often to such an extent as to seriously affect the health and comfort of the individual by interference with urination and by occasioning pain.

Anterior to this organ, in the urethra, is a curious little pouch, the _utriculus_, which corresponds to the v.a.g.i.n.a and uterus in the female.

Just in front of the prostate gland are two small bodies known as Cowper's glands. They secrete a fluid which combines with the seminal secretion.

Female Organs.--The _ovaries_, _uterus_, or _womb_, _Fallopian tubes_, and _v.a.g.i.n.a_ have already been described in part. The external organs of the female are included in the term _v.u.l.v.a_ or _pudenda_. The most superficial parts are the _l.a.b.i.a_, two thick folds of integument. Just within these are two thinner folds, the _l.a.b.i.a minora_ or _nymphae_.

These, together with the _c.l.i.toris_, situated just above, are extremely sensitive organs, being the chief seat of s.e.xual sense in the female.

At the lower part is the opening to the v.a.g.i.n.a, which in the virgin is usually partially guarded by a thin membrane, the _hymen_. This is not always a reliable test of virginity, however, as commonly regarded, since it may be destroyed by disease or accident, and may exist even after the occurrence of pregnancy.

The v.a.g.i.n.a extends from the v.u.l.v.a to the lower end of the uterus, which it incloses, pa.s.sing between the bladder and the r.e.c.t.u.m. The lower extremity of the uterus presents a small opening which leads into its interior. Upon either side, at its upper and larger end, is a minute opening, the mouth of the Fallopian tube. The latter organs extend from the uterus outward nearly to the ovaries, toward which they present a number of small filaments, one of which is in contact with each ovary.

These filaments, together with the interior of the tubes, are covered with a peculiar kind of cells, upon which are minute cilia, or hairs, in constant motion. Very curiously, they all move in the same direction, toward the cavity of the uterus. When an ovum escapes from the ovary in connection with menstruation, it is by these delicate hairs propelled along a filament of tissue to the Fallopian tube, and thence by the same means is conveyed to the uterus. It may come in contact with the zoosperms at any point between the ovary and the lower orifice of the uterus, and thus undergo fecundation.

p.u.b.erty.--For a certain period after birth, the s.e.xual organs remain in a partially developed condition. This period varies in duration with different animals; in some cases being very brief, in others, comprising several years. Upon the attainment of a certain age, the individual becomes s.e.xually perfect, and is then capable of the generative act. This period is called p.u.b.erty. In man, p.u.b.erty commonly occurs between the ages of ten and fifteen years, varying considerably in different climates. In this country, and in other countries of about the same lat.i.tude, p.u.b.erty usually occurs at the age of fourteen or fourteen and one-half years in females, and a few months later in males.

In cooler climates, as in Norway and Siberia, the change is delayed to the age of eighteen or nineteen years. In tropical climates it is hastened, occurring as early as nine or ten years. In warm climates it is no uncommon thing for a girl to be a mother at twelve; and it is stated that one of the wives of Mahomet was a mother at ten.

Other causes besides climate tend to hasten the occurrence of this change, as habits, temperament, const.i.tutional tendency, education, and idiosyncrasy.

Habits of vigorous physical exercise tend to delay the access of p.u.b.erty.