Principles and Methods of Morphometry

Abstract

For obvious reasons organs of the size of the human lung cannot be completely investigated. Every study of the properties of its internal structures will have to be carried out on samples of the tissue, particularly on sections which can be analyzed microscopically. In descriptive morphology it is customary to sample typical regions which are then carefully investigated. This procedure, however, gives no indication of the frequency and distribution of the structures analyzed. It may, thus, lead to an unjustified overestimation of the importance of some peculiarities of the tissue and to a misinterpretation of their significance. For example, the occurrence of internal longitudinal muscle bundles in systemic arteries of the lung was interpreted as a regulating mechanism (“Sperrarterie”) because it was found in connection with anastomoses between bronchial and pulmonary arteries (v. Hayek, 1940; Verloop, 1948; and others). A systematic study of the distribution of such arteries with longitudinal muscle bundles, however, revealed that they were only rarely associated with broncho-pulmonary anastomoses but occurred commonly all along the course of the bronchial arteries (Töndury and Weibel, 1956 and 1958; Weibel, 1958 and 1959). This led to a re-interpretation of the longitudinal muscle bundles as a reaction of the vessel to intermittent stretching by the respiratory movements of bronchi; this hypothesis could be substantiated experimentally (Weibel, 1958). Such misinterpretations due to inadequate sampling procedures may be encountered even more frequently in pathologic studies, in which it is quite customary to study typical lesions.