790 MEDICINE [SYNOPTICAL VIEW. stage, which may be demonstrated, in individual cases, for cancers, are a philosophical necessity for all other in fective diseases that are marked by morphological features, or by structural characters rooted in and growing out of the proper textures of the body. Thus the peculiar skin eruption of small-pox, which is communicable from person to person, along with a distinctive course of fever, must have had pre-autonomous antecedents (not altogether his torically vague) in certain casual conditions of the skin and associated constitutional disturbance, which had re curred and become inveterate, and had so attained to a degree of individuality or a point of autonomy at which they began to be propagated as an organic unit. Again, a second group of infections, exemplified by glanders, bovine tubercle, and syphilis, are rooted in deeper textural pro cesses, which must have been at one time (and may still be) set up by the casual operation of ordinary causes, and at length became the occasion of infective mimicry. It is not so easy to picture (and it is not difficult, with a modern dominant school, to ignore) the casual morbid conditions or ordinary physiological perturbations out of which powerful infections like cholera, typhoid fever, or yellow fever may have arisen ; but if the rise and consoli dation of their autonomy be a subtle or even untraceable history, yet there are diseases, such as dysentery and erysipelas, which are apt to occur both as casual or spontaneous conditions and as specific infections side by side. Ophthalmia is an example of a purulent catarrh which is constantly arising de novo in Egypt from local causes in a non-infective manner, and yet has become, on at least one memorable occasion, a powerful and wide spread infection for British troops returning from that country and for the home garrisons for many years subse quently. Infective pneumonia in cattle, and more rarely in man, is an analogous case. In such an episode we observe the actual rise of the disease-autonomy. Again, all the in fective diseases have degrees of intensity, at one extreme of which there must occur the vanishing point of their in fective property ; and those gradations of infectiveness are nowhere more noticeable than in the relation of cholera to choleraic diarrhoea. Further, the remarkable group of climatic fevers are not communicable from person to person (see MALARIA) ; in that respect, and for the reason that the liability of the patient is anything but exhausted by one attack, they are examples of fevers without autonomy. There is not one of the infections that may not be profit ably studied from the point of view of its autonomy, and of its more or less obscure pre-autonomous stage. That is a point of view from which even the pestilences and other specific diseases may be regarded as coming within the physiological categories. The large residue of diseases, which are more than perturbations of the physiological life, may still be joined by natural descent to the class of simple perturbations, if we can show for them how their autonomy was acquired, or what was their origin us disease- species. There is an established place in the history of medicine, and there ought therefore to be room in the definition of disease, for epidemic outbreaks of purely psychical diseased states, such as the dancing madness (Tanzivutli), and the boys crusades ; the epidemic diffusion of such morbid states is best approached from the point of view of an acquired autonomy (fixed idea) and an infective mimicry. The physiological definition of disease, morbus est vita prxter iiftturam, affordvS no place for parasitic diseases. However, the supplementary formula that has been pro posed to meet the case of diseases existing autonomously in the body, morbus est vivum in vi/ o, will meet the case of parasitic diseases also. According to many patho logist? of the present generation, the whole class of pesti lences, fevers, and specific infectious generally are caused by certain species of minute parasites invading the body ; according to one form of that hypothesis the distinctive characters or specific marks (morphological and other) of those diseases are neither more nor less than the appropriate effects wrought upon the textures and fluids of the body by the respective species of parasites. In this way the great group of infective diseases, which are apt to be the stumbling-block of a scientific definition and logical scheme of disease, are easily disposed of by placing them beside the otherwise insignificant group of parasitic diseases. Whether all or any of those diseases are due in a sense to the invasion of parasites, or wholly caused by parasites, are questions that naturally fall to be settled by a careful sifting of a mass of evidence which has already proved to be peculiarly rich in opportunities for mistake. It may be expected that the facts of infective parasitism and the facts of acquired disease-autonomy will in the end find their place in a common theory of specific diseases, which might be expressed in terms of the physio logical formula morbus est vita prxter naturam with the rider morbus est vivum in vivo. The theory of remedies, which forms the second division of the science of medicine, is chiefly based upon pharmaco logy or toxicology. If pharmacology be considered as not co-extensive with toxicology, it will be taken to be in great part pharmacographia, or the systematic description of articles of the materia medica their source, preparation, physical properties, and the like. Toxicology is in its general sense the investigation of the physiological action of drugs, a science which is largely dependent upon experi ments on the lower animals ; in a more technical sense toxicology relates to the effects of poisons and the art of detecting them (see POISONS). The physiological action of drugs is the key to their therapeutical action. Thera peutics has been defined as " the discovery of the means by which a system of forces competent to eliminate any given perturbation may be introduced into the economy." The adaptation of remedies to diseases is, however, greatly wanting in precision, and continues to be in large part empirical and traditional. It may be objected to the above definition that all diseases are not reducible to the category of " perturbations," and that there is a certain scientific justification for the doctrine of specifics. Besides the articles of the materia medica proper, agencies such as electricity, baths, sea-voyages, and changes of climate generally, enter into the consideration of therapeutics, and two of those form the subject of special departments, viz., electro-therapeutics and hydropathy. Regimen and diet are also important factors in the treatment of disease ; according to a contention of Hippocrates, it was in the dietetic needs of mankind that the medical art had its origin. Subdivisions of Medicine as an Art and DiscApline. The medical art (ars mcdendi) breaks away at once from the unity of the theory of disease. While there is but one body of pathological doctrine for either sex, for every period of life, and for every region and part of the organism, the practical art divides itself into departments and sub- departments. The most fundamental division is into internal and external medicine, or into medicine proper and surgery. The treatment of wounds, injuries, and deformities, with operative interference in general, is the special department of surgical practice (the corresponding parts of pathology, including inflammation, repair, and removable tumours, are sometimes grouped together as surgical pathology) ; and where the work of the profession is highly subdivided, snrgery becomes the exclusive pro vince of the surgeon, while internal medicine remains to
the physician. A third great department of practice is