Abstract
This paper deals with a macroscopical and histological description of the tumors and endocrine glands of two individuals of immature chum-salmon, Oncorhynchus keta (WALBAUM), which were obtained in the course of breeding experiment. The salmon eggs inseminated on November 22nd, 1959 in the Chitose-river, Hokkaido, were transported by air to the Enoshima Aquarium, and reared with cold sea-water until the most of individuals have died of various kind of diseases and accidents.
The proximal pars distalis of the hypophysis of both specimens (A and B) is composed chiefly of acidophils, and the basophils (cyanophils) which seem to be the gonad stimulating cells are meager in number. Accordingly, there found no indication of the yolk formation (vitellogenesis) in the majority of ovarian eggs. The secretory phase of the hypothalamic neurosecretory cells is in a state of low activity, and the amount of neurosecretory substance stored into the neurohypophysis is small. The thyroid gland shows a hypofunctioning figure, and the normal appearance of the corpuscles of STANNIUS is detected. In the B-specimen the normal feature of the adrenal cortical tissue is also encountered.
It is very interesting to find a remark able swelling in the head kidney of the A-specimen, macroscopically. This tumorous development is constructed from a great, deal of lymphocytes which have derived from multiplication of the parenchymatous cells, curled collagenous fibers and reticulum. In several places the tumorous tissues are collapsed owing to the necrosis and changed into serous or lacteal substance, and, finally, an indication of formation of cystic spaces and lacunae, varying in size, aredetected.
A large tumorous growth is also found in the right side of posterior part of the B-specimen, which suppresses the digestive tracts, particularly the rectum, markedly. Just beneath the lateral line of the fish, a severe ulcer which is due to the degeneration and necrosis of the growth is produced. Accordingly, the inside of the growth is exhibited. This tumor is diagnosed as the small round-cell sarcoma developed in the inter-trunk-muscular connective tissue. The tumorous cells, round in shape, invade everywhere into the bundles of muscles, and brought about the transformation of muscles into connective tissues. In the inside of the growth a large lacuna is produced, containing the lacteal substance under the degeneration and necrosis of the tissues.
