As a result of all this work, we pride ourselves on the advance
in knowledge of infectious disease, which the germ theory has brought
us, and yet we are utterly and completely ignorant of the two things
about infectious diseases which are, perhaps, the two things most worth
knowing. No man has conceived the way in which the parasites of
disease first fastened themselves on the animal body, a specific
parasite to a specific animal. In other words, we have no idea of
how diseases first began. LIt may be that if these tiny organisms
existed before Man, as they undoubtedly did, they must have undergone
considerable modifications before they were able to invade him, and
live and multiply within him. For ought we know, the first vegetation
that clothed the earth may have given rise to the first disease germs.
Mammals eating the vegetation, would unconciously take these germs of
disease into their systems. Whereas most of these germs Would be
digested and cast out, the day might dawn when a single germ might
survive the digestive process of the mammals, suit itself to the new
conditions, and breed new races of germs which eventually invaded Man.
On the other hand, the first mobile forms of life may have given rise
to their own germs of decay, which waited until the cycle of life was
finished before they operated as nature's scavengers and reduced the
body to its natural element, so that it could be again absorbed by
earth and air. As the forms of life became higher, the germs of
decay probably changed to suit the new environment. Instead of waiting
until the cycle of life was finished and then acting on the dead body,
they may have advanced that comparatively tremendousstep which them
attacking life itself, in order to obtain food. The original germs
of decay may have given rise to the more highly developed germs of
disease, which strove to provide food for themselves, instead of waiting
for it to be provided.
Secondly, no man has conceived why diseases, distributed over a wide area and in many should vary in virulence from time to time, why, for instance, a relatively mild infection such as influenza should suddenly devastate the whole world. It is easy to say that human resistance varies, but that is only to restate the problem in
terms of which we know nothing. On these high topics of medicine we know as much, and as little, as Hippocrates.
Moreover, if we turn to definite diseases, there are many conditions, and those among the most important, of which our ignorance is almost complete. Thus, of the very common and painful diseases, muscular rheumatism and rheumatoid arthritis, we hardly know anything and our remedies are little more effective than those used in olden times. The common cold - economically the most important disease, not
excluding cancer and tuberculosis - has a vast literature, but the physician is almost helpless in its presence and can but let it run its course. Measles, influenza and whooping-cough have become more deadly of late years, and we have still no clear line of treatment for them. Nor have we any real insight into the nature of cancer. Those who reach advanced age have no better chance of life than they had two hundred years ago, though it is true that now there are many more people who reach advanced age. Above all it must be remembered that the great majority of deaths are caused by diseases theoretically preventable. There is a natural term of life to which it is desirable all should attain. Yet, most of us will surely die a violent
death, as truly as though struck down by a felon's hand. Death from disease is an unnatural and a violent death.
Thus life is ever a struggle. On all sides Man is menaced by myriads of foes, visible and invisible. The seen foes are recognised and feared, but the unseen foes are little known to the multitude, and barely understood by the scientist.
The greatest protection of these microbes is their invisibility to the human eye, and their great danger to mankind lies in the power of
some species, for each individual to reproduce its own, the rapidity with which they multiply and the fact that they are indirect feeders, and can obtain sustenance direct from the oxygen, nitrogen and other
elements of the soil.
Up to within comparatively recent times, Man carried on his battle against the deadly germs unconsciously. So the germ armies have
gone on massacring humanity, fighting under a cloak of invisibility which we are only now tearing aside. The great European War, with
its appalling slaughter, bulks large in the history of the world. It has created a tremendous impression on mankind. Yet the great war, and
all other wars, are mere affrays compared with that greater war which mankind has been fighting for ages. This greater war is the battle
between germs and Man. It is never-ending, but goes on day and night, and the people who have been slain by the germs, innocent men, women and children, total thousands of millions.
For untold ages Man has fought against Nature and battled with the foes that are seen. He has become the most highly developed of living
creatures, wielding powers both wonderful and terrible. From afar he can launch death an kill his fellow-man. He can strike .the creatures
of the world dead in their tracks. Yet Man himself, for all his powers, eventually dies. While he lives,he has to fight for his
existence against the foes that are visible, and the invisible foes generally drag him down at last. Man,who has vanquished the greatest
of living creatures, generally succumbs in the end to the tiniest of living organisms, the microbes of disease. So may the importance of
the discovery of the Germ Origin of Disease be appreciated.