A second difficulty is in getting the drug to produce its effect at the right point.  A few diseases, as we have noticed, are produced by bacteria which distribute themselves almost indiscriminately over the body; but the majority are somewhat definitely localized in special points.  Tuberculosis may attack a single gland or a single lobe of the lung.  Typhoid germ is localized in the intestines, liver, spleen, etc.  Even if it were possible to find some drug which would have a very specific effect upon the tuberculosis bacillus, it is plain that it would be a very questionable method of procedure to introduce this into the whole system simply that it might have an effect upon a very small isolated gland.  Sometimes such a bacterial affection may be localized in places where it can be specially treated, as in the case of an attack on a dermal gland, and in these cases some of the germicides have proved to be of much value.  Indeed, the use of various disinfectants connected with abscesses and superficial infections has proved of much value.  To this extent, in disinfecting wounds and as a local application, the development of our knowledge of disinfectants has given no little aid to curative medicine.

Very little success, however, has resulted in the attempt to find specific drugs for specific diseases, and it is at least doubtful whether many such will ever be found.  The nearest approach to it is quinine as a specific poison for malarial troubles.  Malarious diseases are not, however, produced by bacteria but by a microscopic organism of a very different nature, thought to be an animal rather than a plant.  Besides this there has been little or no success in discovering specifics in the form of drugs which can be given as medicines or inoculated with the hope of destroying special kinds of pathogenic bacteria without injury to the body.  While it is unwise to make predictions as to future discoveries, there seems at present little hope for a development of curative medicine along these lines.

Vis medicatrix naturae.

The study of bacterial diseases as they progress in the body has emphasized above all things the fact that diseases are eventually cured by a natural rather than by an artificial process.  If a pathogenic bacterium succeeds in passing the outer safeguards and entering the body, and if it then succeeds in overcoming the forces of resistance which we have already noticed, it will begin to multiply and produce mischief.  This multiplication now goes on for a time unchecked, and there is little reason to expect that we can ever do much toward checking it by means of drugs.  But after a little, conditions arise which are hostile to the further growth of the parasite.  These hostile conditions are produced perhaps in part by the secretions from the bacteria, for bacteria are unable to flourish in a medium containing much of their own secretions.  The secretions which they