NEOPLASMS involving the ovary are common in the fowl (Olson and Bullis, 1942 ; Campbell, 1945). The great majority faR into one or other of two categories, namely adenocareinomatous growths in various stages ofdifferentiation from the frankly anaplastic type to the sclerosing tumour, or, secondly, lymphomatous growths associated with the leucotic complex, e.g., lymphocytoma, fowl paralysis tumour, aleukaemic lymphoid leucosis, etc. Most of these lymphoid growths should not be classified as ovarian tumours, since in view of the generalized nature of the leucotic process it is usuaRy impossible to be certain whether they are primary in that organ or not. They are mentioned simply because of the frequent Teference in avian pathological literature to " lymphoid ovarian tumours." In human pathology, besid6s-the common adenocareinomatous types of ,ovarian tumour, several other rarer forms are recognized as follows: Brenner tumour (o6phoroma folliculare) : granulosa-cell, thecal, and luteal tumours arrhenoblastomas ; dysgerminomas. A survey of the hterature deahng with neoplastic disease of the fowl shows the apparent extreme rarity of such tumours. Seifried (1923) recorded a Brenner tumour of the fowl and compared it with its human counterpart, a'nd Friedgood and Uotila (I 94 1) detailed 5 cases of-ovarian " tumours " associated with virilism

THE original purpose of this investigation was to study the effects of implanting various tumnours affecting the fowl into the fertile egg.A survey of the literature revealed the rather surprising fact that apart from the Rous I sarcoma (Rous and Murphy, 1911), and a few leucosis cases (Pierce, 1942), no attempt has been made to grow spontaneous neoplasms of the chicken in fertile eggs.There is a high incidence, relative to disease in general, of spontaneous neoplasia in the fowl. Campbell (1945), in a survey extending over five years, found the relative average incidence to be 18'7 per cent in the breeds examined, the minimum and maximum figures for specific breeds being 10-3 per cent and nearly 39 per cent.During this survey a number of chicken tumours were studied which bore a close morphological resemblance to known virus-associated growths. In view ofclaims by various authors (Taylor, 1943; Heilman and Bittner, 1944; Hungate, Snider, Taylor and Thompson, 1945) that mammalian tumours can be easily cultivated in the yolk-sac of the chick embryo, and that a virus-like factor associated with mammary carcinoma of mice has been directly demonstrated by this method, it was thought desirable to apply similar methods to the study of spontaneous chicken tumours.The advantages of using fertile eggs for such cultivation experiments are many. The egg with the developing embryo represents an enclosed stable biological system in which implanted tumours or inoculated viruses can grow under optimum conditions of sterility, controlled temperature and nutritive environment. Also the embryonic membranes quickly provide a vascular bed from which tumour cells can obtain their blood supply. It was argued that if mammalian tumours grow so well in the chick embryo, then turnours derived from autologous tissues should grow at least as well, or perhaps even more readily.One of the disadvantages associated with laboratory animals used for tumour transplantations, etc., is a natural immunity due to the presence of antibody, either resulting from sub-clinical infection, or produced by the animal in response to inoculation with a virus-associated tumour. Also Carr (1943) has shown an immunity to the Rous I sarcoma in a certain strain of chickens which is apparently not due to serum antibodies. Apart frvm the fact that any laboratory animal can only be used for experiments with tumours of that particular species (with * Part of this work was done while the writer was on the staff of the Royal (Dick) Veterinary College, Edinburgh.

1. In the male fowl spontaneous repair of the liver, damaged by repeated doses of the alkaloids of Senecio jacobaea L., takes place extremely slowly, if at all.2. Females subjected to the same treatment tend to recover. 3. In both sexes, but particularly in the male, massive doses of stilboestrol continuously absorbed from pellet implants initiate and speed up liver regeneration.4. The hypothesis is advanced that the impaired ability of the damaged liver to conjugate and inactivate oestrogen is advantageous in so far as the raised oestrogen level stimulates repair processes in that organ.

Images Figs. 9-12 Figs. 1-4 Figs. 5-8

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