PATHOLOGY ( from Gk. r(10os, pathos, disease + Xoyla, -login, account, from Xl-yew, legein, to say). The study of disease as a prov ince of scientific knowledge; pathological physi ology. Disease is well defined as 'the expression of the sum of abnormal cell activities' (Schmans). Such activity disturbs the regular cell life in one of three directions: nutrition. function, or multiplication. It is evident. then, that pathology is equally with physiology a de partment of biology.
Many theories of disease and its causation are found in the history of medicine. Athenams, of Attalia (A.D. 69), was the founder of the pneu matic pathology. Ile held that there is a cer tain spiritual principle, the pneuma, which reaches the heart by way of the respiration and is thence driven through the whole body. When working regularly, and mixed with warmth and moisture, it ()evasions health. When mixed with warmth and dryness it occasions acute diseases. When mixed with cold and moisture it produces the phlegmatic diseases. When mixed with &dd and dryness it eauses melancholy. Ile also claimed that in febrile diseases the humors of the body became corrupted or putrefied. This putridity, he asserted, was a process within the fluids by which they exhaled much water.
Galen (130-e.201) elaborated and advanced the Immoral pathology of (e.460 357 Ile selected four fluids, or hu mors, of the body as the primary seats of dis ease: blood, phlegm, yellow bile, and black llealth he conceived to be the due combination, or 'crisis,' of these; while illness he considered was the result of a disturbance of this condi tion. During favorable progress of disease, these humors underwent a change, or `eoction,' which was taken as a sign of returning health and as a preparation fnr the 'crisis,' when an expulsion of morbid matter occurred. The immoral path ology was long in vogue. Sylvius (147S-1535) and Boerhaave (1668-173S) elmmpioned a new pathology. They asserted that the iatro-chemical 'aeridities' of the fluids played a most important role. They classified acid, saline, oleaginous, glutinous. alkaline, and mixed 'acridities.' which
were supposed to originate in the food and to be especially active in chronic diseases. Glisson (1597-1677) advanced the theory of 'irritability.' attributing it to both solids and liquids. Life itself was considered to be mann (1660-1742) originated the `solidist path ology.' He claimed that disease was "a marked disturbance in the movements of the solids and the fluids." In these disturbances the solids are the active and the fluids are the passive agents.
Excessive movement produces 'spasm' and defec tive movement produces `atony.' Disease, he admitted, "might be due to alteration in the humors, and especially to a gradual thickening of the vessels, which tends at once to hinder their free circulation and to prevent the ex cretion of waste products." His four main sources of disease were, therefore, spasm, atony, altered humors, and deficient excretion. Barthoz (born 1734) launched the mystic and vague vitalistic pathology. He assumed the existence of a `vital principle,' neither soul nor body. Dis ease he asserted to he the effort of the vital prin ciple to resist harmful agencies, or to be due to "a morbid idea manifesting itself by alterations in sensibility, abnormal movements, or an aber ration in those acts which regulate the chemical constitution of the humors." It was reserved for Virehow in 1S5S to enun ciate clearly and elaborate convincingly the cel lular pathology, now accepted the world over, and forming the basis of a universal view of the organs and the diseases which affect them.
The complex human organism may be reduced to very simple elements—the cells and the inter cellular substance to which they give origin. All parts of all organs and tissues are composed of cells or products of cells. Blood and lymph are tissues, differing from muscular or fibrous tis sues in that they have fluid intercellular sub st.unee. Cells are the conductors of vital func tions, normal or abnormal. Their condition changes with age, disease, and fatigue on the one hand, and reparation and nutrition on the other.