We now know the origin of many diseases which formerly were enveloped in mystery. Can we remove them? That is the next task. Hygiene will in the future busy itself with this great question. It has, it is believed, already made many cities proof, or almost proof, against cholera and yellow fever. It will try to make them proof against other contagious diseases also, and it will without doubt succeed. But its work will not then have been accomplished. We may avoid the causes of disease and still be puny creatures. Our great task will be the building up of bodies equal to the needs of our environment. This we have, in a small way, already begun to do—imitating the ancient Greeks—in our schools of physical culture, where the body can be trained up to its best, and also in our laboratories for psychological research, in which the relation of mind and body are being carefully investigated, where every subject connected with every function is being studied, even weariness, anger, hope, despair, drink, food, sleep, the weather, and their effects on function. The results of such knowledge will prove beyond a doubt that the health of the body, as well as of the mind, is of the highest importance for success in life, for happiness and usefulness, and that we can do much to secure both.
My own personal hope for the future of human health lies in the evolution and spread of this gospel of hygiene.
Hygiene interests itself in all that relates to human well-being. It may be defined as the ethics of the body—the science of true living. It promises health to all who obey its laws. It makes no such promise to those who disregard them. In the future, no doubt, a higher average of health will be the result of our ever-increasing knowledge; and whenever we are able and willing to apply this knowledge to our own bodily and mental conduct we shall be amply rewarded. This much we can safely promise, but no more. On the contrary, the violators of hygienic laws will, with their offspring, suffer in the future as in the past, and that suffering will be in the form of pain, disease, degeneration, premature death.
This may seem hard to many who are sensitive to the pains and sorrows of the world, and some have gone so far as to attribute to the author of nature, the unknown cause of all things, a character anything but good. But this is a very erroneous way of looking at the subject. To discuss it fully we should have to consider the question of the mystery of evil, which cannot be done here. Suffice it to say, the creation, the evolution of the race, is by law. Causes produce their legitimate results. If it were not so, our sufferings might be far greater, and no progress would result. Let us be thankful that nature is as it is, and let us do our best to put our lives in harmony with it. By so doing, we may in the end attain all that we strive for.
THE GERM PLASM; ITS RELATION TO OFFSPRING.
The germ plasm is a most interesting and remarkable substance. It must be interesting, for everything which relates to life and reproduction is interesting. It must be remarkable, for out of it, under proper conditions, remarkable results are produced. Although our knowledge of its nature is very imperfect, yet let us not on this account refuse to try to understand what little is known.
In the first place, the germ plasm of animals which reproduce sexually is composed of two germ plasms—that of the male, and that of the female. That of the male is called the spermatozoon (pronounced sper´ma-to-zoön). It is sometimes called spermatozoid; the plural is spermatozoa. It is exceedingly small, the smallest of any cell in the body, and has the power to move from place to place. These cells are produced in enormous numbers, and so far as they have been observed under the microscope they differ considerably in power of movement and in perfection of development. Considering their small size, they must make a very long journey to find the ovum; and if they were only few in number, they would rarely succeed; but existing in large numbers, for there are millions of them produced in each sexual act of the male, some of them are pretty sure to do so, and, probably in most cases, it would be those most vigorous and capable of making the journey most direct and in the least time.
That of the female is called the ovum, or egg; plural, ova. Only a small number are produced, when compared with the number of the male spermatozoa, but there are quite enough for the ends they are to serve. They have not the same power of movement, though they do move somewhat as the amæba does. They are also very much larger than the male cells.