274 



HYPOPHYSIS AND GONADOTROPHIC HORMONES 



(1956), applying the Bielchowsky-Gros 

 technique to the adenohypophysis of the 

 duck, demonstrated in the capsule and 

 throughout the gland the presence of an 

 autonomic neural formation composed of 

 large strands of nerve fibers replete with 

 ganglion cells and end formations adjacent 

 to parenchymal cells. The presence of even 

 these minor neural contributions to the pars 

 distalis has been vigorously denied by 

 Green (1951b). He was not able to identify 

 such perivascular fibers in the pars distalis, 

 although they were found in the pars tu- 

 beralis. 



It is significant that all attempts at in- 

 fluencing pituitary secretory function by 

 sympathectomy or by proximal stimulation 

 of the cervical sympathetic trunk have 

 yielded either negative or eciuivocal findings 

 (Friedgood and Pincus, 1935; Friedgood 

 and Cannon, 1940). Although bilateral re- 

 moval of the superior cervical or stellate 

 ganglia of the sympathetic system in fer- 

 rets has been shown to abolish (Abrams, 

 Marshall and Tliomson, 1954) or delay 

 (Donovan and Van der Werff ten Bosch, 

 1956) the estrous response to added illumi- 

 nation, the latter authors believe this may 

 be accounted for on the basis of an indirect 

 effect ; namely, a diminished amount of light 

 impinging on the retina. All the operated 

 animals showed a marked Horner's syn- 

 drome, i.e., globe recession, ptosis, and nar- 

 rowing of palpebral fissure. 



From the foregoing evidence, the conclu- 

 sion seems clear that the regulation of the 

 pars distalis by secretomotor nerves must 

 be slight, if indeed there is such regulation. 

 All the instances of identification of nerve 

 fibers are open to doubt for the reason that 

 the staining methods do not adequately 

 differentiate nerves from reticular connec- 

 tive tissue fibers. It is to be noted also that 

 by use of phase contrast microscopy in 

 combination with staining i)roccdures. 

 Green (1951b) found no fibers in the rabbit 

 or human pars distalis that could with cer- 

 tainty be identified as nerves. 



B. TIIK MKOIAN EMINENCE AND 

 THE I.VFUNDIBULAR STEM 



The eminentia has become a focus of 

 interest in attemi)ts to understand neuro- 

 endoci'iiic I'clationsliips, because this area is 



contiguous with both the hypothalamus and 

 the hypophysis. It is present in vertebrates 

 from amphibians to mammals, and its 

 structure is quite uniform throughout the 

 birds and mammals (Green, 1951a; Wing- 

 strand, 1951b; Nowakowski, 1951). The 

 median eminence is comprised of an inner 

 ependymal zone, a middle coarse-fiber zone 

 made up of the axons of the supraoptic- 

 hypophyseal tract, and a so-called glandular 

 zone at the surface. The name of the latter 

 was derived from the density of the capil- 

 lary skein on its surface — it has also been 

 termed the peripheral or marginal zone. 



The glandular zone contains the capillary 

 loops of the primary portal plexus (de- 

 scribed below) , perpendicularly arranged fi- 

 bers extending from cells in the ependymal 

 zone and some fibers of nerve cell origin. The 

 latter lie along the base of the glandular 

 zone from which recurrent loops are said to 

 extend toward the surface (Wingstrand, 

 1951b; Nowakowski, 1952; Assenmacher 

 and Benoit, 1953a, b). Stutinsky (1951) 

 and Vazquez-Lopez and Williams (1952) 

 believed that they have demonstrated fibers 

 from the tractus hypophysius crossing the 

 marginal zone to enter the pars tuberalis, 

 thence to follow the course of the portal 

 veins toward the pars distalis. The exis- 

 tence of such fibers is denied by Rumbaur 

 (1950), Wingstrand (1951a), and Palay 

 (1953a). The innervation of the glandular 

 layer is, as Wingstrand (1951a) states, the 

 key to the postulated control of the pars 

 distalis by a neurovascular mechanism. For 

 birds he states: "No nerve fibers have been 

 seen leaving the eminentia but invariably 

 turn back when they reach the surface. ..." 



The glandular zone contains a fiocculent 

 colloid that is demonstrable with the azan 

 trichrome stain, but there is no agreement 

 as to whether this material stains selectively 

 with chronic alum liematoxylin (Gomori- 

 l)ositive) like tlic neurosecretory substance 

 in tlie tractus hypophysius. Benoit finds 

 ahmidant Gomori-positive material in the 

 glandular zone in the duck, whereas Wing- 

 strand's examination of a great variety 

 of birds i'e\-eal('d faintly positive reacting 

 colloid only in a restricted area in the rostral 

 portion of the median eminence. He doubted 

 that it is similar to the heavily staining 

 neuroscci'ctoi'V substance in the supraoptic- 



