Surgery

and for the screening of cases in which further examination under the electron microscope might be merited. The light microscope allows the heights of the villi and the depth of the glandular layer to be measured, and the limits of normality to be defined on a quantitative basis. The electron microscope reveals abnormalities in the microvilli of mucosal epithelial cells. The mildest changes consist of shortening and fusion of the microvilli and a lessened electron-density of the atypical cytoplasm. Since these changes have been seen in specimens of mucosa which appear to be normal under the dissecting and the light microscope, they are assumed to be related to the earlier stages of the disease, and their significance is discussed in the light of this view.