Abstract
The authors have conducted histopathological studies on various types of the avianleukosis complex"9?"). The materials used for these studies were morbid chickens wlaichhad occurred spontaneously in Japan since 1950.In this paper, histopathological investigation was carried out on 78 chickens whichwere believed to have been infected naturally with a disease identical with what hadbeen known by the name lVareks disease and broken out on 25 poultry farms mainly in1969. The birds were layer chickens of foreign-produced strains from 37 to 191 days ofage. For histological examination, as many samples as possible were collected fromvarious parts of organs, including the central and peripheral nervous systems and theeyes. Furthermore, the authors reexamined the specimens dealt with in their previousreports, part II (neural lyrnphomatosis)20) and part III (ocular lymphomatosis)21).In the present studies, the following particulars were examined: the character ofproliferating cells, the distribution and severity of lesions, and the relationship betweenthe termination of the birds used and the type of proliferating cells. The proliferatir-ugcells were Iymphocytic and divided into three types, large, medium, and small, chieflyon the basis of size. The main Iesion of the disease in question was composed of pro-liferating cells. Such cells were also present frequently in blood vessels. Lesions weredistributed widely in organs, including the central and peripheral nervous tissues, eyes, mesenteries, and adipose tissues, located in the whole body. The lesions were variablein severity. Generally speaking, this disease had a tendency to be more malignant when pro-liferating cells of large and medium sizes were predominant in the cellular element ofeach lesion.From the findings thus obtained, especially those on the character of the proliferat-ing cells, it was considered that the disease dealt with in this paper should be called"lymphatic leukemia", and that "neural lymphomatosis" and "ocular lymphomatosis", which had been described in the authors previous reports, parts [120) and [1121), shouldbe regarded as diseases of the same category as lymphomatic leukemia. Moreover, it wasthought that "avian visceral lymphomatosis", which was described in the authors pre-vious reports, parts I") and VI3), should be called "germ cell sarcoma".
