not to interfere so as to destroy the course of natural compensations; but seeks by dietetical, hygienic, and climatic influences, here by the removal of excitants, there by methodical stimulation of the matter-changes of the nervous system—to put the organism into a condition to overcome the pathological disturbances. To use such measures, carefully adapted on principles of scientific observation and enlarged knowledge of the course of disease to the most diverse conditions, continually to furnish a closer support to the natural compensations and adaptations that is one of the ways to which the healing art must turn in order to enlarge its scope.
Since we know that already developed pathological processes can be only imperfectly or not at all affected by art, it should be our more inflexible purpose to guard against their beginning, to recognize the causes of disease, and render them harmless. But this purpose must be comprehended in its widest sense; it should not be confined to the prevention of infectious diseases alone, or to mere measures of sanitary policy, but should also include specific means of cure. Thus, the treatment of malarious disease with quinine is to all appearance etiological. The changes that have already taken place in the blood-cells and the spleen are not reversed by quinine, but the plasmodia of malaria are in some way destroyed, and then the disease may be cured.
The hope is not unjustified that in a nearer or further future we shall learn to nullify by specific means the promoters of disease in many other infections. After nullifying the irritating causes, the processes of Nature may be relied upon to complete the cure. It is possible that this advance will be perfected incidentally, as has happened with quinine and malarious disease, and with salicylic acid and rheumatism. There is also good ground here for the hope that methodical research will be rich in results. The fruitful investigations of numerous contemporary laborers permit much to be expected. And though the conflict of opinions sways hither and thither, and although the knowledge that has been gained relates only to diseases of animals, there is no vital reason for supposing that the same results will not also be reached for man.
The efforts of the present are turned in three directions: to cure bacterial diseases that have already become clinically visible; to make infections harmless while in their incubatory stages; and especially to ward off infection. The last-named object is the farthest-reaching one. It can be attained in two ways: by sanitary protective measures against epidemics, and by conferring immunity on the individual organism, of which vaccination for small-pox is a typical example. Securing artificial immunity by inoculation, and its scientific basis, are now in the full flow
