REPRODUCTIVE ENDOCRINOLOGY IN BIRDS 



109/ 



tion where the j)osterior distal centriole is 

 located, is over 100 /x long. The tail has a 

 smooth appearance except for the last two 

 fji. It consists of an axial filament surrounded 

 by a thin sheath, which, however, seems 

 absent for the last 2 fi, and shows the fibrils 

 caused by the absence of the thin sheath 

 which surrounds the rest of the axial fila- 

 ment. The axial filament itself consists of 11 

 fibrils. Nine of these fibrils, the L fibrils, are 

 about 450 A in diameter and are not easily 

 destroyed by distilled water. Two M fibrils 

 are easily destroyed so that no estimate 

 could be made of their diameter. Grigg and 

 Hodge (1949) have speculated that the L 

 fibrils might be the motor elements for the 

 sperm whereas the M fibrils might act as 

 controls for the L fibrils. An extensive re- 

 view of the problem of sperm motility is 

 contained in the chapter by Bishop. 



B. ENDOCRINE REGULATION OF 

 TESTICULAR ACTIVITY 



1. The Pituitary Gland 



The general concepts of the morphology 

 of the pituitary gland with respect to func- 

 tion and of the physiology of the pituitary 

 gland have been discussed in detail in the 

 chapters by Purves and Greep. It seems thus 

 desirable to discuss here only those aspects 

 which substantiate general principles found 



to be true also for the avian pituitary and 

 to mention in what respects the avian pi- 

 tuitary differs from the mammalian pitui- 

 tary. A large part of the description of mor- 

 phology has been taken from the excellent 

 comparative account of avian pituitaries by 

 Wingstrand (1951). 



The avian pituitary (Fig. 18.8) lacks an 

 intermediate lobe in all species investigated. 

 The epithelial stalk, a vestige of the connec- 

 tion between adenohypophysis and its point 

 of origin in the oral epithelium, is more 

 prominent in some species than in others, 

 but it lacks glandular activity in all the 

 species. Within the pars distalis a distinc- 

 tion can be made between caudal and ce- 

 phalic lobes. The Ai cells or dark-staining 

 acidophils (dark red with azocarmine) are 

 restricted to the caudal lobe (Rahn and 

 Painter, 1941; Wingstrand, 1951; Matsuo, 

 1954; Mikami, 1954), whereas the Ao cells 

 are restricted to the cephalic lobe (Rahn 

 and Painter, 1941; Wingstrand, 1951; IMat- 

 suo, 1954). 



According to Wingstrand (1951), Ai cells 

 and chromophobes are sometimes difficult to 

 distinguish. Mikami (1955) states that the 

 thyrotrophs, which he distinguishes by their 

 positive periodic acid-Schiff (PAS) reaction 

 are also restricted to the cephalic lobe. Wing- 

 strand ( 1951 ) concluded that the following 

 avian-mammalian homologies exist: the 



Fig. 18.8. Pituitary of a goose (Anser anser) according to Wingstrand (1951). (From K. G. 

 Wingstrand. The Structure and Development of the Avian Pituitary. CWIv Gleerup, 1951.) 



