GENERAL PATHOLOGY. Of prime importance to the pathologist is the study of disorders of circu lation, whether (1) hyperwmia, arising from ex cess of supply or diminished escape of supply of blood; or (2) a decrease of supply of arterial blood; o• (3) hemorrhage. (see BLEED ING) ; or (4) (edema (q.v.) ; or (5) thrombosis (q.v.), under which is to he considered embolism (q.v.), with consequent necrosis o• relief by an astomosis.
(q.v.) is a local death of tissue, due to circulatory disorder, thermic action, or in flammation. A regressive disorder of the life of cells in which there is diminished nutritive and functional derangement is degeneration. Ten forms occur. The degeneration may be parenehymatous (or albuminous)• fatty, mucous, colloid, amyloid, hyaline. glycogenic, o• hydropic, or may appear in the' form of petrification or pigmentation. Some of these forms of degenera tion are described in the article Bructir's Dts EASE. In some forms of degeneration products of imperfect metamorphosis accumulate within the cells. In others, necrotic cells and tissue elements o• fo•eignn material collect between the cells. In still others, there is a gradual degeneration of the cell elements and a deposi tion in their place of a new substance. Atrophy (q.v.), on the contrary, is essential loss of substance without deposit of pathological or foreign material. Each component part of the tissues shrinks in volume. Yet atrophy may be accompanied by deposits of various kinds, and in such cases coexists with degeneration, as in artcrio-sclerosis (q.v.). Defective innervation, exhausting diseases, disuse, long-continued mod erate pressure, or certain drugs may he the cause of atrophy, in different tissues, and these causes must be weighed by the physicians in determin ing pathological conditions in the course of treatment of a diseased person.
Among the progressive processes, or those in which the vital activity of the organism is actually increased, the most important are the reproduc tive. Inherent in every cell is the tendency for reproduction. Stimulus of various kinds awak ens this innate tendency, which results in pro duction of new tissue of various forms. Closely
allied to the reproductive energy is the stimulus and the power to repair, to replace lost parts. Should the process of rebuilding go on to no excess of mere replacement, or should regular physiological growth be excessive, and the result be an increase in size as well as an increase in number of the elements. the condition is termed hypertrophy (q.v.). Under the influence of bac teria or ehemical agents or unaseertained causes, and accompanied by pronounced vascular dis turbance. a certain progressive process results in infiammatinn (q.v.). Still another progressive process results in the formation of neoplasm, or new growths, constituted of tissues of a difrerent kind from those adjacent and developing at their expense. Most of these formations are consid ered under Tumoa.
With this preliminary knowledge of the proc esses at work, it is usual• in taking up the study of special pathology, to consider first the dis eases of the blood, next those of the lymphatic tissues, then those of the various systems with their organs—respiratory, gastrointestinal, urinary. and reproductive—am] then the dis eases of bones and of joints, of voluntary mus cles• of the brain and its membranes, of the spinal cord and its membranes. and of the peri pheral system of nerves.
To bacteria are ascribed the production of lesions. and they certainly influence chemical and physiological processes, locally and systemie ally. To their agency are ascribed pneumonia. diphtheria. cholera. leprosy. bubonic plague (qq.v.), etc. Animal parasites also play an important rule in the production of pathologic conditions. Among them are the A ma ba coll.
the Thrmatozoon etc. It is believed.
though not yet demonstrated, that. to some proto zoa are due scarlet fever, measles, and smallpox.
There are also parasitic wo•nn.s which produce diseases such as tapeworm, lumbrieoides, filaria (TIN.), etc. The special pathology of the dif ferent diseases is under the proper title for each disease.
Consult: Green and 51 timy, Pathology and Morbid Anatomy (Philadelphia. 1900) : Stengel.
Textbook of Pathology (ilt, 1901): Seim/ails and Ewing. Pathology and Pathological Anatomy (ib., 1902).