At a certain period in the life of the youth he undergoes a change by which he acquires powers, which qualify him to take part in the perpetuation of his kind. This change is the period of puberty. It is distinguished by a number of physical alterations, the most significant of which is the secretion of a fecundating fluid.

Yet we must not be understood to say that this is a prompt or sudden change. On the contrary, it is slow, extending over many years, attended by a completion of growth and a ripening of all the physical powers. Only when all these various processes are matured does the male reach the period of virility, that period which is the proper time for him to fulfil the duties which nature has imposed on those features peculiar to his sex. We cannot too earnestly impress on all the truth of this fact. Through ignorance of it, or neglect of it, untold misery is constantly brought upon the young, and the race itself shows the sad results of an infraction of this rule. Let us therefore define more minutely these two phases of life.

When the boy passes to the condition of youth he leaves behind him the characteristics of childhood. The skin becomes coarser and less delicate, the muscles firmer and more distinctly marked, the voice loses its childish treble, the vocal apparatus enlarges and emits a harsher sound, the bones harden, the " wisdom teeth" appear, various parts of the body become covered with a soft down which gradually becomes rougher and thicker, and those organs peculiar to his sex enlarge.

Not less remarkable are the mental changes. Unwonted desires and sensations, half understood and confusing, awake in the mind impulses to which he has been a stranger, vague longings after he knows not what, sudden accesses of shame-facedness in circumstances where he had ever been at ease, a Restlessness, and a wilfulness, indicate to the observing eye the revolution which is going on within. Perilous moment for the boy! Dangers of which he has no knowledge, which he could not understand were they explained to him, yet which will imperil all his future life and all his other faculties, are around him.

The proper age at which puberty should come varies from twelve to eighteen years, as it is influenced by many surrounding conditions. One of the most important of these is climate. Travelers have frequently observed that in tropical countries both the sexes arrive at maturity earlier in life than in temperate or cold countries. This explains the early marriages which are customary in those localities, and which do not appear to exert the injurious influence on the offspring which is almost constantly observed in temperate climates from premature unions. In Abyssinia and the shores of the Red Sea, which are the hottest parts of the globe, it is no unusual sight to see boys of fifteen and sixteen who are already fathers. And what is even more singular, this precocity does not appear to react on the constitution, but according to the observations of an English surgeon during the Abyssinian campaign, the masculine functions are retained with exceptional vigor to very advanced years.

In Lapland, Northern Russia, and Siberia the young men reach the age of eighteen and nineteen years, before their sluggish constitutions undergo the changes incident to puberty, and even then it is rare that their passions are violent or long retained.

In our own country, the usual and healthy age of puberty is from fourteen to fifteen years, varying a year or two more or less as influenced by circumstances which we shall proceed to mention. One of these is hereditary tendency. This is constantly observed as hastening or retarding by a your or two the development of both sexes. It is to some extent connected with race, as it is found that negroes are more precocious than whites, and boys of southern parentage than those of northern. This is readily seen to be traceable to the influence of climate just referred to.

The temperament is also a controlling influence. Light-haired, stout, phlegmatic boys are longer in attaining the age of puberty, than those of nervous and nervo-bilious temperaments.

Occupation and habits have also much to do in the matter. As a general rule, the more vigorous, the more addicted to athletic exercise, the more accustomed to out-door life, and to active pursuits, the slower will be this change in approaching. This statement may be unexpected to many ; they may think that vigorous health is precisely what nature would wish to assist her to complete this profound and mysterious transformation in the constitution. To all such we have to tell of a law sanctioned by the researches of all physiologists, proven by the daily experience of the physician, and which wo shall have occasion hereafter to refer to frequently, for it contains the solution of many a vexed physical and social problem. This law teaches that there is a constant and a direct antagonism between the highest perfection of the individual and the exercise of the masculine function; or, to quote the words of one of the most eminent writers on physiology, Dr. Carpenter, "The Development of the Individual and the Reproduction of the Species stand in an inverse ratio to each other."

The constitution, by which we mean the mass of morbid or healthy tendencies inherited from parents, consequently has very considerable weight in determining the time at which the change will take place. In accordance with the physiological law just quoted, it is very generally found that boys with weak, nervous, debilitated constitutions are apt to be precocious; and those gifted by their parents with sturdy limbs and a powerful frame remain boys much longer.