361 P ATHOLOGY (irddo?, Aoyo?, the doctrine of disease or (lit.) of that which is suffered) holds a peculiar place among the natural sciences. Although it is laid down, in the opening sentences of the Hippocratic treatise De prism medicina, that the medical art, on which all men are dependent, should not be made subject to the influence of any hypothesis (such as that of the four cardinal qualities, hot, cold, moist, and dry), that the care and cure of the sick should not be subordinated to pathological ieory theory, but should be guided by experience ; yet the prac- dprac- titioners of medicine have at no time been able to dispense with theory, not even those avowed followers of the Hippo cratic tradition who, while they professed a kind of quiet ism amidst the rise and fall of systems, have none the less been profoundly influenced by theory at every step of their practice. The position of Cullen is the only rational one : " You will not find it possible to separate practice from theory altogether ; and, therefore, if you have a mind to begin with theory, I have no objection. . . . To render it safe, it is necessary to cultivate theory to its full extent." 1. PROGRESS AND SCOPE. The progress of pathology hitherto has been exactly parallel with the progress of philosophy itself, system suc ceeding system in genetic order. No other department of biological science has shown itself so little able to shake off the philosophical character, or to run in the career of positivism or pure phenomenalism. This unique position of pathology among the natural sciences is doubtless owing to the fact that it is a theory of practice, a body of truth and guess-work existing for the benefit of a working pro fession which is daily brought face to face with emer gencies and is constantly reminded of the need of a reasoned rule of conduct. It is idle to attribute the philosophizing habit in medicine, or the habit of system -making, to an unscientific method in past times. The extremely various points of view from which the problems of diseased life are approached in the very latest and most authoritative writings are an evidence that the difficulty is really in herent in the subject-matter. The positive progress of the biological sciences does not essentially depend on the philosophical conception of life as action and reaction ; but the notion of action and reaction comes to the front in every page of a patho logical treatise, and at every step of practice. In con sidering the forms of diseased life, if not in the study of living things themselves, we. are constantly driven back to that ultimate analysis. The influences from without, which make up aetiology or the doctrine of causes of disease, assume a position in medicine the urgency or immediate interest of which far exceeds that of the bio logical problem, "the correspondence between life and elation its circumstances." The standing difficulty in pathology > aetio- h as b een its relation to aetiology, or the relation of the )gy> ens morli to the agens morbi. One of the most singular ways of meeting the difficulty is that of Paracelsus, who boldly perpetrated the paradox : " Ens ist ein Ursprung, welches Gewalt hat, den Leib zu regiren." The five classes of entia of Paracelsus are a composite catalogue, of which (1), (2), and (5) stand for influences from without, and (3) and (4) for spontaneities, dispositions, or liabilities within. From time to time the centre of interest has been shifted to within the body, as in the "animism" of Stahl, in the " vitalism " of the school of Montpellier (end of 18th century), and in the "cellular pathology" of Virchow. A discussion of the inherent difficulty of holding the balance fair between that which is "exopathic" in disease and that which is " endopathic " may be read in Virchow s article, " Krankheitswesen und Krankheits- ursachen," written in reply to objections that the cellular pathology was inadequate. " What I wished to treat of in the Celhdar Pathology" he says, " was the behaviour of the elements of the living body in the usual kinds of illness, or, to put it more briefly, the history of the element ary processes of disease. Upon that basis, it seemed to me, the doctrine of the nature of disease should be built. The respective causes I adverted to only now and then ; thus I spoke of poisons, and even fungi had a place in the cellular pathology, although a very modest one. If the Celhdar Pathology had ever pretended to be a general pathology it would have contained also the whole of aetiology." Thus far Professor Virchow writing in 1880. If we now turn to a text-book of the same date, which does bear the title of General Pathology, that of Professor Cohnheim, we find pathology defined as "an explanatory science which seeks (1) to discover the causes of disease, and (2) to ascertain the esoteric connexion subsisting among disease-manifestations." It is only (2) that forms the subject of Professor Cohnheim s two volumes; aetiology, he remarks, is absolutely without limits. It " comes into relation with" cosmical physics, meteorology, geology, sociology, chemistry, botany, and zoology ; from these sciences it gets its subject-matter. In the general patho logy of Cohnheim, accordingly, aetiology is omitted ; and with it are omitted many of the problems underlying the philosophical systems of the past, which have "only an historical interest," as well as much of the natural history of disease. General pathology, he says, knows no other direction and no other order than physiology, "and accordingly we shall take up successively, and in the same order as physiology would take them, the pathology of the circulation, digestion, respiration, tissue -nutrition, and the like " (the pathology of the nervous system is not included in the two volumes). Without adducing other instances of eclecticism in the contents of modern patho logical text-books, it will be convenient to give a brief notice of the latest attempt at a philosophical scheme of diseases, the Elemente der Pathologic of liindfleisch, 1883. There are certain groups of symptoms, says Rindfleisch, Riml- which recur with the uniformity of a type in the most fltisch s various diseases, depending as they do upon one constant r factor, the human body and its structural and functional tendencies. The larger number of maladies do not arise autochthonously or "under a whole skin," they are gener ated by certain morbific causes ; and it is the variety of causes that corresponds to the variety of disease-species, or to those ever -changing sequences and coexistences of symptoms in which the experienced eye of the practitioner learns to distinguish one disease from another. The mor bific cause is an invasion upon the normal course of our life, usually a strong and forcible interference with the physical and chemical constitution of a particular part of the body. The disease as a whole stands for the effects of this interference, and these effects flow in part from the nature of the morbific cause and in part from the nature of the body which suffers. That which is uniform in these effects flows from the nature of the sick body ; that which is various flows from the variety of morbific causes. It is I above all the seat of the disease, its duration, the sequence and combinations of the type-groups of symptoms which I are determined by the morbific cause. Only this vary- | ing element can be used to distinguish one disease from , another. Therefore there is only one truly natural prin- XVIII. 46 scheme.
