“ In the process of inflammation we have a series of reactions on the part of the tissues, and fluids of the body, to counteract the ill effects of irritation or injury, to get rid of the cause, and to repair its results. Injury and loss of tissue are usually followed by repair, and both the destructive and reparative changes are, as a rule, classified under the term inflammation. The irritants may be bacteria and their toxins, or they may be mechanical, chemical or thermic. ”

“ Seldom has it happened, since the discovery of the law of gravity, that so profound an impression has been made upon the scientific world at large as by the revelation of the part played by germ-life in nature; seldom has any discovery been fraught with such momentous issues in so many spheres of science and industry. ”

“ When we consider that tuberculosis, diphtheria, cholera, tetanus, typhoid fever, anthrax, malaria and a host of other contagious diseases have each been proved to be of parasitical origin, an idea may be conveyed of the range of the subject. The living organism may be regarded as constantly engaged in a warfare with these silent and apparently insignificant messengers of destruction and death, with the result that too often the battle ends in favour of the attacking enemy. ”

“ Our range must embrace a much wider area—must comprise, in fact, all living matter—if we are ever to arrive at a scientific conception of what disease really means. Hence not only must the study of our subject include the diseases peculiar to man and the higher animals, but those of the lowest forms of animal life, and of plant life, must be held equally worthy of attention. ”

“ Since pathology is the science of disease, we are met at the very threshold by the question: What is disease? This may Health and Disease. best be answered by defining what we understand by health. What do we mean when we talk of a healthy organism? Our ideas upon the subject are purely arbitrary, and depend upon our everyday experience. Health is simply that condition of structure and function which, on examination of a sufficient number of examples, we find to be commonest. ”

“ Continuous Over-pressure.—The tissues of an animal or plant are all under a certain pressure, caused, in the one case, by the expulsive action of the heart and the restraint of the skin and other elastic tissues, and, in the other case, by the force of the rising sap and the restraint of the periderm or bark. Under this normal amount of pressure they can live and grow. But whenever, from any cause, the degree of pressure which they are naturally intended to withstand is surpassed, they fail to nourish themselves, become granular, die, and, falling to pieces, are absorbed. ”

“ In recent years the successful experimental transplantation of new growths, occurring sporadically in white mice and rats, into animals of the same species, has thrown a fresh light on all the features of malignant growths. From these experiments it is shown that cells taken from these growths and introduced into animals of the same species give rise to a cancerous growth, whose cells have acquired unlimited powers of proliferation. They are direct lineal descendants of the cells introduced, and are in no way formed from the tissue cells of the host in which they are placed and grow. ”

“ Increased work thrown on to a tissue may produce hypertrophy, but, if this excessive function be kept up, atrophy will follow; even the blacksmith's arm breaks down owing to the hypertrophic muscle fibres becoming markedly atrophied.
From these causes a certain shrinkage is liable to occur, more evident in some parts of the body than in others. Thus the brain falls off in bulk, and the muscles become attenuated, and in no muscle is this more notable than in the case of the heart. A tendency to pigmentation also develops in certain tissues of the body, such as the nerve and muscle cells. ”

“ A plant or animal in perfect health is more resistant to parasitical invasion than one which is ill-nourished and weakly. Of a number of plants growing side by side, those which become infected with moulds are the most weakly, and an animal in low health is more subject to contagious disease than one which is robust. Each organism possesses within itself the means of protection against its parasitical enemies, and these properties are more in evidence when the organism is in perfect health than when it is debilitated. ”

“ When the pancreas is excised in an animal, or when it is destroyed in man by disease, grape-sugar appears in the urine. The gland is supposed to secrete a ferment, which, being absorbed into the portal circulation, breaks up a certain portion at least of the grape-sugar contained in the portal blood, and so prevents this overflowing into the circulation in general. The transplantation of a piece of living pancreas into the tissues of an animal, thus rendered artificially diabetic, is said to restore it to health. ”

“ When a nerve-trunk is separated from its central connexion, the distal portion falls into a state of fatty degeneration (Wallerian or secondary degeneration) . That special trophic nerves, however, exist throughout the body, seems to be a myth. It is much more likely, as Verworn alleges, that the nerves which influence the characteristic function of any tissue regulate thereby the metabolism of the cells in question—in other words, that every nerve serves as a trophic nerve for the tissues it supplies. ”

“ The foregoing hypotheses have all sought the origin of new growths in some intrinsic cause which has altered the characters of the cell or cells which gave rise to them, but none of them explain the direct exciting cause. The parasitic hypothesis postulates the invasion of a parasite from without, thus making a new growth an infective process. Many cancer-parasites have been described in cancerous growths, including bacteria, yeasts and protozoa, but the innumerable attempts made to demonstrate the causal infective organism have all completely failed. ”

“ At no time has so much been done to advance our knowledge of diseases of the nervous system as during the last thirty years of the 19th century. The localization of function in the cerebral and in the cerebellar cortex has doubtless been the main cause of this progress, and has proceeded pari passu with an extended insight into the structure and connexions of the parts concerned. The pathology of aphasia, as worked out by a combination of the experimental, the pathological and the anatomical lines of inquiry is a favourable example of what has been accomplished. ”

“ Our starting-point in this, as in all departments of biological study, must be the biological unit, and it is to the alterations to which this is subject, under varying conditions of nutrition and stimulation, that the science of pathology must apply itself. Man can never be the only object of appeal in this inquiry. The human organism is far too complex to enable us to understand the true significance of diseased processes. ”

“ There are conditions in which we have an abnormal increase in the tissue elements but which strictly should not be defined as hypertrophies, such as new-growths, abnormal enlargements of bones and organs due to syphilis, tuberculosis, osteitis deformans, acromegaly, myxoedema, &c. The enormously long teeth sometimes found in rodents also are not due to hypertrophy, as they are normally endowed with rapid growth to compensate for the constant and rapid attrition which takes place from the opposed teeth. ”

“ The irritant may be chemical, as is seen in the skin cancers that develop in workers in paraffin, petroleum, arsenic and aniline. However close the relationship is between chronic irritation and the starting of cancer, we are not in a position to say that irritation, physical or chemical, by itself can give rise to new growths. It may merely act locally in some way, and so render that part susceptible to unknown tissue stimuli which impart to the cells that extraordinary power of proliferation characteristic of new growth. ”

“ To heredity, as an indirect or predisposing cause, has probably been assigned too great importance, and the many facts brought forward of the relative frequency of cancer in members of one family only justify the conclusion that the tissue-resistance of certain families is lowered. ”

“ If the eyeball be kept perfectly clean and no organism be admitted from the outside then ulceration will not follow. If, on the other hand, any pathogenic organisms be present the results are disastrous because the tissue, deprived of its nervous trophic supply, has greatly lessened resistance. The bed-sores which follow paralysis of the limbs are often quoted as proof of the direct trophic action of the nerve-supply upon the tissues, yet even here the evidence is somewhat contradictory. ”

“ So long as the epidermis of animals remains sound, disease germs may come in contact with it almost with impunity, but immediately on its being fissured, or a larger wound made through it, the underlying parts, the blood and soft tissues, are attacked by them. ”

“ Medicine and surgery have never been slow to appropriate and apply the biological facts of pathology, and at no period have they followed more closely in its wake than during the last quarter of the 19th century. ”

“ If the demand be for the red cells owing to loss from hemorrhage or any of the anaemias, the fatty marrow is rapidly replaced by cellular elements; this is mainly an active proliferation of the nucleated red cells, and gives rise to the erythroblastic type of marrow. If the white cells be required, as in local suppurating abscess, general septicaemia, acute pneumonia, &c., there is an active proliferation of the myelocytes to form the polymorpho-nuclear leukocytes, so that we have in this condition a leucoblastic transformation of the fatty marrow. ”

“ Where the malnutrition is the effect of poorness in the quality of the blood, the results are of course more widespread. The muscles suffer at an early period: they fall off in bulk, and later suffer from fatty degeneration, the heart being probably the first muscle to give way. Indeed, all tissues when under-nourished, either locally as the result of an ischaemia, or generally as from some impairment of the blood, such as that prevailing in pernicious anaemia, tend to suffer from fatty degeneration ”

“ Many cells throughout the body contain this ferment. The soluble soaps which are probably conveyed by the blood will be quickly taken up by such cells, synthetized into neutral fats, and stored in a non-diffusible form till required. The fat in this condition is readily recognized by the usual microchemical and staining reactions. As fat is a food element essential to the carrying out of the vital energies of the cell, a certain amount of fatty matter must be present, in a form, however, unrecognizable by our present microchemical and staining methods. ”

“ The acute bed-sore is, in some cases, a true trophic lesion occurring, as it may, on parts not subjected to continuous pressure or irritation. Trophic disturbance in the nutrition of the skin may be so great that a slight degree of external pressure or irritation is sufficient to excite even a gangrenous inflammation. Again, a fractured bone in a paralysed limb often fails to unite, while another in the opposite sound limb unites readily, and an ulcerated surface on a paralysed limb shows little healing reaction. A salivary gland degenerates when its nerve-supply is cut off ”

“ A knowledge of the bacteriology of scrofulous affections of bone and joints, such as caries and gelatinous degeneration, has shown that they also are tubercular diseases that is to say, diseases due to the presence locally of the tubercle bacillus. At a very early period it was held by Virchow that the large cheesy masses found in tuberculosis of the lung are to be regarded as pneumonia infiltrations of the air-vesicles. Their pneumonia nature has been amply substantiated in later times; they are now regarded simply as evidence of pneumonia reaction to the stimulus of the tubercle bacillus. ”