Excerpt from A Treatise on Hygiene and Public Health, Vol. 2 of 3 Few branches of medical science can be said to have received, within the last twenty-five years, greater attention, and to have developed more largely within a comparatively short period, than the knowledge of the nature of infectious diseases. Not only have many disorders, belonging to this class and for a long time suspected as belonging to this group, become well under stood in their nature, their mode of origin and spread, but others, not previously suspected to be communicable diseases at all, have been Shown to appertain to this class. To quote for each of these one instance: typhoid fever, though for a long time assumed to be a communicable disorder spread ing from the sick to the healthy by the evacuations, had not, prior to the researches of Budd, Snow, Simon, Buchanan and others, been proved to be of this character, and though some authorities, like Murchison, pleaded for the possibility of a spontaneous origin, the weight of evidence was in favour of its being a specific disease, which, like all specific diseases, can only arise from a previous Specific disorder of the same kind. By the researches of more modern investigators, notably Buchanan, Ballard, and Thorne Thorne, its mode of Spread has become well understood, and by their investigations its nature - viz. That of a specific communicable disease - been definitely settled. As examples of diseases not previously suspected to belong to this group but now known to be so, we may quote tetanus, and epidemic or croupous pneu monia. Of both these diseases recent research has shown that they are of an infectious character, that in both there exists a specific virus which, finding entrance into a healthy individual, is capable of setting up the disorder. These examples we could easily multiply. Nay more, we could Show, on the one hand, that as regards a number of disorders for whose specific nature there existed until quite recently very slender evidence, there are now definite and exact experimental grounds for asserting their specific nature, e.g. Anthrax, tuberculosis, septicaemia, and erysipelas; on the other hand, by ascertaining the exact nature of some of these disorders, others formerly not distinguished from them have been shown to have a separate existence and to be different from them in their pathology, symptoms, course, and causation. Thus, for instance, malignant anthrax has been Shown to be a perfectly separate disorder from symptomatic anthrax woolsorters' disease (malignant pustule) to be a separate disease from some forms of ragsorters' disease tuber culosis to be different from other chronic lung diseases, to which it bears a distant pathological semblance. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.