Nervous diseases also run in families. Not that any one nervous disease necessarily descends in any family, but nervous diseases generally are hereditary. They are associated, as I told you just now, with the nervous temperament Persons of such families, who do not actually suffer from nervous diseases, are very frequently of a marked nervous temperament.

These are some of the most common examples of hereditary diseases.

Now, what is to be done for hereditary disease ? In the first, place it is clear that any one who belongs to a family in which one of these diseases is known to be hereditary, must do all he can to avoid the conditions which will favour the development of that disease. Persons who belong to families in which consumption or scrofula exists, must avoid living in damp houses, must avoid, as far as they can, inferior food and bad hygienic conditions generally. Persons who belong to families in which nervous diseases are prevalent, must avoid the conditions which I mentioned just now as conditions which should be avoided by persons belonging to the nervous temperament.

But the most important precaution of all is that persons who belong to families in which any kind of disease is hereditary, have no right to marry into families in which the same disease is prevalent. This is done continually, because people are thoughtless about this, one of the most important matters concerning them.

If there is any tendency to disease in your family, and you marry into a family in which that same disease exists, your children are almost certain to suffer from that disease in the worst possible form. If there is a tendency to nervous disease in your family, and you marry into a family in which nervous diseases are prevalent, it is very likely indeed that your descendants will furnish a very large number of inmates to the lunatic asylums ; people ought to think of these things a very great deal more than they do. Not only are tendencies to disease hereditary, but a tendency to long life is hereditary, and that you will see follows almost necessarily from what I have said. If mischief in the organs of the body is likely to descend, and if likenesses descend, it follows that perfection of the various organs of the body is transmitted in families, and so long life is hereditary. But there is another reason why long life is hereditary, and that is, that long-lived people have a kind of contempt for persons who are not long-lived, and they rarely marry into any families that are not long-lived families, and so this tendency to long life is increased, and that makes it still more markedly clear, and it has been observed over and over again that long life is hereditary.

That we are subject to different diseases, and to different kinds of disease, at different times of our lives, was pointed out by Hippocrates, who divided man's life into various periods, and showed that each period had its own diseases belonging to it Now you will see at once that this must be so, when you consider how different we are at different periods of our lives. In a very young stage of life, for instance, there is no bone; it is only cartilage or membrane; as we go on getting older, bone becomes formed, bones become consolidated, some of them become soldered together, parts of the body become harder; and this process of hardening begins from the very beginning and goes on until we reach the most perfect state of our life, and while it goes on to that state it is' advantageous; we are getting our organs to work more and more in sympathy with one another, and their action is becoming more and more confirmed. Then for a long period we appear to be stationary, but we are not stationary at all; degeneration of tissue begins ; some of our tissues are getting rather harder as time goes on, and we get gradually into the period of decay, the period of decline; some of the tissues get harder than they ought to be for the work they have to do; they get stiff, and calcareous matter gets deposited in various parts of the body when it ought not to be. The walls of the great arteries get less elastic and do not recoil upon the blood, the circulation becomes enfeebled, the tissues of the body have been gradually becoming degenerated, and so we pass on, until, if we are not taken off by disease of one kind or another, we die by the actual stoppage of one of the organs which is essential to our life, by the actual stoppage of our lungs or heart; so that you see, that at different periods of our life we are different beings altogether, and so it need not surprise anybody, that at those different periods of our life we are subject to different diseases. Now the periods of life have been divided differently by various authors; but the division which is the best, the division which we shall take, is the division given to us by that great observer of human nature, William Shakspeare. I do not know that it was really Shakspeare's, yet I do not know that it was not; it is generally put down to him. When looking into the question a short time ago, I came across a quotation from a medical work of the time of Shakspeare, published in the same .year as his "As You like It," or a year before, in which the divisions of Shakspeare of the life of man are given, and in which a certain treatment for the different periods of life is prescribed ; so that if it was not Shakspeare's division, it was a division which was suggested to him, and which he adopted.

Shakspeare, in his " As You like It" (act ii. scene 7), makes Jacques say,-

" All the world's a stage, And all the men and women merely players : They hay© their exits, and their entrances; And one man in his time plays many parts, His acts being seven ages. At first, the infant* Mewling and puking in the nurse's arms; And then the whining school-boy, with his satchel, And shining morning face, creeping like snail, Unwillingly to school. And then, the lover, Sighing like furnace, with a woeful ballad, Made to his mistress' eyebrow. Then a soldier, Full of strange oaths and bearded like the pard, Jealous in honour, sudden and quick in quarrel, Seeking the bubble reputation, Even in the cannon's mouth. And then, the justice, In fair round belly, with good capon lined, With eyes severe, and beard of formal cut, Full of wise saws and modern instances; And so he plays his part The sixth age shifts, Into the lean and slipper'd pantaloon, With spectacles on nose and pouch on side, His youthful hose well saved, a world too wide For his shrunk shank ; and his big manly voice, Turning again toward childish treble, pipes And whistles in his sound. Last scene of all.