THAT the central nervous system is involved in feather release has been reported by King (1920), Weaver (1936) and Ostmann (1962). The autonomic nervous system also contributes to feather release (Langley, 1904; Ostmann et al., 1963). The results of administration of various classes of drugs on feather release also indicate that the nervous system is involved in this phenomenon (Sturkie et al., 1958; Klose et al., 1961, 1962; Knapp and Newell, 1961; Huston and May, 1961; Ostmann et al., 1963).

A PREVIOUS report by Ostmann, Ringer and Tetzlaff (1963) indicated that anesthetics, sympathetic and parasympathetic blocking agents, and tranquilizing drugs caused the feather to loosen within its follicle. These workers did not clarify the exact role played by the muscles and wall of the feather follicle in feather release.

THE effect of drugs on the muscles of the feather follicle has received comparatively little attention. Langley (1904) used atropine, curari, apocodine and adrenalin and observed no effects upon the movements of the feathers. In contrast, nicotine, injected intravenously, resulted in a strong depression of the feathers of the body. A subsequent dose, however, failed to add any further effect upon the feathers. He further reported that strychine, following curari, caused irregular erection and depression of the feathers for one to two minutes.

A SEARCH of the literature reveals very little information on the anatomy of the feather follicle and its immediate surroundings. Most of the information available on this subject is in regard to the muscles which move the feather and was reported in the nineteenth century. The muscles of the feather follicle were first described by Nitsch (1840), who reported that four separate muscles were usually attached to the follicle of each contour feather although sometimes six and more rarely five were present. Seuffert (1862) observed that contour feathers of the trunk region usually had two to four separate muscles. He stated that the muscles were unstriated and attached to the follicle by elastic tendons. These muscles were observed to course from the lower part of one follicle to the upper part of an adjacent follicle. Similar observations were made by Helm (1884).

ARTERIOSCLEROSIS of aves is similar to that seen in humans (Katz and Stamler, 1953). The normal spontaneous development of avian arteriosclerosis and the ease with which cholesterol can induce this condition have promoted the study of arteriosclerosis in birds.

GATES (1946) records a number of human pedigrees showing a high incidence of hypertension which suggested a relatively simple mode of inheritance. More recent studies, however, suggest a complex mode of inheritance and moderate or relatively low heritability. Pickering (1955) who reviews the more recent data indicates a heritability of from 20–23 percent for blood pressure in humans. Alexander, Hinshaw and Drury (1954 Alexander, Hinshaw and Drury (1956) who selected and bred hypertensive rabbits were able to increase level of pressure in the progeny but did not estimate the heritability. Sturtevant (1953) was unable to change mean pressure in rats after two generations of selection for hypertension, but he did report a significant decrease in the variability of pressure.

CONFLICTING evidence has been published on the growth of the oviduct following gonadotrophin administration to prepuberal chicks. Stimulated oviducal growth, if it occurs, implies an active source of estrogen. The specific tissue elaborating estrogen in the bird has not been established (Taber, 1948). In line with mammalian data, the ovarian cortex, if not the maturing follicle itself, might be the source. However, the ovarian hypertrophy following gonadotrophic treatment appears to be confined to proliferation of medullary tissue, with little, if any, follicular development (Domm and Van Dyke, 1933; Asmundson et al., 1935, 1937; Domm, 1937; Uotila, 1939; Nalbandov and Card, 1946; Taber, 1948; and Das and Nalbandov, 1955). Thus, further information on the oviducal and ovarian response of immature chicks to gonadotrophins might provide clues relative to the unsettled question of the source of estrogen.

THE physiological factors involved in the formation of the albumen, shell membranes and shell of the avian egg have been the subject of numerous researches and controversies. For reviews consult Burmester (1940), Romanoff and Romanoff (1949), Warren (1949), and Sturkie and Polin (1953).