1114 



SUBMAMMALIAN VERTEBRATES 



lactin which cause metabolic disturbances 

 that interfere with development of the rudi- 

 ment. 



Miller (1938) utilized the occurrence of 

 spermatogenesis in the rudimentary gonad 

 in an ingenious procedure for identifying 

 the sex chromosome. Study of actively di- 

 viding spermatocytes in a normal testes 

 and in a rudimentary gonad revealed that 

 the 5th largest chromosome, a V-shaped one, 

 was not paired in the rudiments, but was 

 paired in the testes from a normal male, 

 thereby proving that this chromosome is the 

 sex chromosome. 



Development of the rudimentary gonad 

 after ovariectomy occurs in ducks and song- 

 birds (Nalbandov, 1958) but not in turkeys 

 (Domm, 1939). In addition to those that 

 can be attributed to the activity of the rudi- 

 ment, other sex abnormalities sometimes 

 occur. Crew (1923) documented a case in 

 which a bird laid eggs and subsequently 

 "sired" offspring. The bird had two testes 

 with vasa deferentia and a diseased ovary 

 and thus was a true hermaphrodite. Hutt 

 (1937) reported a case in which a chicken 

 was first more like a pullet, later showed 

 male characteristics and produced sperma- 

 tozoa (incapable of fertilization) , and later 

 looked more like a female. The bird on au- 

 topsy had a testis and vas deferens on the 

 right and an ovary and oviduct on the left 

 side. This bird was a gynandromorph, as 

 was evident from the feather pattern which 

 was light on the left side (one sex chromo- 

 some) , dark on the right (two sex chromo- 

 somes), and from the fact that the right 

 side exceeded the left in size. The cases re- 

 ported by Crew (1923) and Hutt (1937) 

 show that "sex reversals" can occur with- 

 out involvement of the rudimentary female 

 gonad. Benoit (1950a) hsted other instances 

 in which the same phenomenon occurred. 



2. The Ovary 



The ovary is attached to the body wall by 

 a short mesovarium. In the quiescent state 

 the ovary is a small, flat, yellow organ with 

 small (< 1 mm.) follicles. In the active 

 state it is a large organ composed of 5 to 6 

 large follicles filled with yellow yolk and a 

 larger number of smaller follicles filled with 

 white yolk. The large follicles are graded in 



size whereas the smaller follicles are more 

 uniform. In addition to these follicles one 

 may find atretic follicles ; in the early stages 

 of atresia they look somewhat like a shriv- 

 eled balloon but later may become small, 

 dark yellow, flabby masses. After ovulations 

 the ovary also contains ruptured follicles. 

 These ruptured follicles disappear rapidly 

 in the fowl and the rook, Corvus /. frugilegus 

 L. (Marshall and Coombs, 1957), but they 

 persist until the end of the breeding season 

 in pheasants. Counts have been made of 

 these follicles to determine the egg produc- 

 tion of pheasants (Kabat, Buss and Meyer, 

 1948; Buss, Meyer and Kabat, 1951). 



The ovary is innervated by the nerves 

 from the abdominal and pelvic plexuses and 

 from the posterior continuation of the sym- 

 pathetic trunk (Bradley, 1950). It receives 

 its blood from the ovarian artery which is 

 usually a branch of the left renolumbar 

 artery but occasionally is a branch of the 

 dorsal aorta (Nalbandov and James, 1949). 

 The ovarian artery divides and sends 2 to 

 4 branches to each follicular stalk. Spiral 

 arteries provide the main blood supply in 

 the wall of the follicle ; these spiral arteries 

 constrict when the ruptured follicle col- 

 lapses and thus little if any bleeding occurs 

 at ovulation. The ovarian venous system 

 is much more extensively developed than 

 tlie arterial system. Nalbandov and James 

 (1949) classified the venous system of the 

 follicles in 3 layers: (1) a capillary network 

 in the theca of the follicle that drains by 

 venules into (2) a complex network periph- 

 eral to the first layer that drains into (3) a 

 third venous layer consisting mainly of a 

 few large veins that drain into the follicular 

 stalk. The large veins from different follicles 

 anastomose and drain into either the ante- 

 rior or the posterior ovarian vein both of 

 which empty into the vena cava. 



Histologic examination of the ovary re- 

 veals the presence of the left adrenal and 

 the epoophoron embedded in the stroma 

 (Biswal, 1954). The large follicles (Fig. 

 18.10) consist of the very vascular theca 

 folliculi, the basement membrane, the gran- 

 ulosa, and the vitelline membrane which 

 surrounds the yolk. An area which macro- 

 scopically seems free of blood vessels stands 

 out sharply in the follicular wall. This area. 



