Of the patient and unremitting toil demanded of the investigator in this realm of the infinitely little; of the skill in manipulation, the fertility of resource, the scrupulous exactness of experiment that are absolutely prerequisite to success; of the dangers that attend investigations which deal with noxious germs, every one who knows anything of the subject has some conception, but those alone can have full comprehension who have themselves attempted to follow the devious and delicate pathways of bacteriology. But the goals to which these pathways lead have a tangibility that give them a vital interest for all the world. The hopes and expectations of bacteriology halt at nothing short of the ultimate extirpation of contagious diseases. The way to that goal is long and hard, yet in time it will be made passable. And in our generation there is no company of men who are doing more towards that end than the staff of that most famous of bacteriological laboratories the Pasteur Institute. THE VIRCHOW INSTITUTE OF PATHOLOGY Even were the contagious diseases well in hand, there would still remain a sufficient coterie of maladies whose origin is not due to the influence of living germs. There are, for example, many diseases of the digestive, nutritive, and excretory systems, of the heart and arteries, of the brain and nerves, and various less clearly localized abnormal conditions, that owe their origin to inherent defects of the organism, or to various indiscretions of food or drink, to unhygienic surroundings, to material injuries, or to other forms of environmental stress quite dissociated from the action of bacteria. It is true that one would need to use extreme care nowadays in defining more exactly the diseases that thus lie without the field of the bacteriologist, as that prying individual seems prone to claim almost everything within sight, and to justify his claim with the microscope; but after that instrument has done its best or worst, there will still remain a fair contingent of maladies that cannot fairly be brought within the domain of the ever-present "germ." On the other hand, all germ diseases have of course their particular effects upon the system, bringing their results within the scope of the pathologist. Thus while the bacteriologist has no concern directly with any disease that is not of bacterial origin, the pathologist has a direct interest in every form of disease whatever; in other words, bacteriology, properly considered, is only a special department of pathology, just as pathology itself is only a special department of general medicine.