Abstract
In ultrastructural observations on the midgut of Bombyx larvae utilizing conventional ultrathin sections, there were problems of interpretation with respect to the three dimensional ultrastructure of the nuclear pores, the mitochondria-filled cytoplasmic projections of the goblet cells, and the secretory globules from the columnar cells. This paper reports the results of studies on these problems using an improved frozen section method. The shapes, sizes, and distribution of the nuclear pores were determined. The three dimensional ultrastructure of the mitochondria-filled cytoplasmic projections of the goblet cell was clarified. The three dimensional morphologies of organelles such as the Golgi apparatus, endoplasmic reticulum, microvilli, secretory globules, cell junctions, and basal infoldings in both columnar and goblet cells are described. The utilization of the frozen section method for the electron microscopic study of insect tissues is discussed.
