Abstract
The histopathological investigation was undertaken in an attempt to know the susceptibility and its local difference of the midgut cells of silkworm larva, Bombyx mori L., on which the treatments such as (1) refrigeration, (2) virus feeding, and (3) virus feeding after refrigeration were performed immediately after the fourth ecdysis.
The results were summarized as follows.
(1) When the silkworm larvae are refrigerated, the larvae fall into gattine-like disease, and the cytoplasm of the midgut cylindrical cell become to have many vacuoles. and the nuclei begin to swell up remarkably in several days. It is interesting to see that the similar figures are observed in the study of gattine by PAILLOT (1930).
(2) In the experiment of virus feeding, the cytoplasmic polyhedron did not appear, but the similar histopathological changes mentioned above in (1) were also observed.
(3) In the case of combined treatment with virus feeding andrefrigeration, the cytoplasmic polyhedron appeared. The changes seen in the experiments (1) and (2) were not seen in nucleus, though the degeneration and disappearance of nuclei were often noticed after completion of polyhedron formation.
(4) The histopathological changes in cytoplasm and nucleus are usually observed at first in the posterior division of the midgut epithelium and then appear inmiddle and anterior ones.
(5) It may be said that the cell susceptibility to the pathogenic injuries differs according to the treatments and the division of midgut epithelium, and in the latter case the susceptibility of the cells are the most intensive in the posterior division compared with the cells of the middleand anterior divisions.
