CENTRAL CONTROL OF PITUITARY SECRETION 



TABLE I . Volumes of the Whole Pituitary Gland, and oj Its Different Lobes in Rabbits Submitted to Simple 

 Stalk Section, and Stalk Section with the Insertion of a Plate Between the Cut Ends 



Normals (21) 



Simple stalk section (12) 



Stalk section with a plate (28) 



Whole Gland 



I00.0±4.3* 

 62 .4±2 .9 

 73.8±4.2 



Pars Distalis 



ioo.o±5.6 

 67-5±3-9 

 82.9±5.4 



Pars Intermedia 



ioo.o±6,9 

 ioo.8±8.i 

 110.8+7.3 



Neural Lobe 



IOO.Ort4.6 

 26.6±2 . I 



25.7±i.6 



Median Eminence 



IOO.O±6.2 



i50.8±i3-8 

 206 . 2 ± I o . 8 



Volumes for normal rabbits expressed as 100%. 



Number in parentheses represents number of animals in group. 



* Standard error of mean. 



Data from Campbell & Harris (50) 



and well maintained, several weeks or months after 

 cuttina; the stalk. The pars distalis of the drake 

 atrophies to about 70 per cent of normal \olume after 

 cutting the hypophysial portal vessels (tractotomy) 

 (22), and that of the ferret shrinks to 80 to 95 per cent 

 of normal voluine (81). More detailed measurements 

 have been made in the rabbit (50), the results of 

 which are given in table i. In this form the pars 

 distalis atrophies to about three quarters of normal 

 size. In considering whether the functional defi- 

 ciencies of the pars distalis produced by stalk section 

 are consequent upon this degree of ischemic necrosis 

 and atrophy, two points arise, a) The same degree of 

 atrophy of the pars distalis occurs in the ferret (81) 

 and rabbit (50), and probably in the rat (153), 

 whetiier the stalk is simply sectioned or is cut and a 

 plate inserted between the cut ends. However, loss of 

 anterior pituitarv function is marked and constant 

 onK in animals in which a plate has been correctly 

 inserted between the stalk ends and is not detectable 

 in many animals following simple stalk section. 

 b) Studies of the functional loss following varying 

 degrees of incomplete hypophysectomy (118, 197, 198, 

 282, 321, 349) show that about 30 per cent of the 

 normal volume of the pars distalis is sufficient to 

 maintain normal anterior pituitary function, that 10 

 per cent will maintain some gonadotrophic activity 

 and may result in only minor degrees of adrenocorti- 

 cotrophic and thyrotrophic deficiency, and that some 

 adrenocorticotrophic function persists unless hy- 

 pophysectomy is complete. From the above data it 

 seems clear that anterior pituitary deficiency following 

 stalk section is not due to ischemic atrophy but is 

 probably due to interruption of some specific physio- 

 logical stimulus to the ^land derived from the hy- 

 pothalamus. 



Gonadotrophic Secretion After Pituitary Stalk Section or 

 Transplantation. Early studies on the effect of pituitary 

 stalk section have been reviewed (156). It is sufficient 



to give here as an example some of the work reported 

 on one species, the rat. In this form section of the 

 hypophysial stalk was found to result in lengthened 

 estrous cycles (44, 280), in gonadal atrophy in male 

 and female animals (41, 350, 351), and in normal, 

 lengthened or absent estrous cycles (74, 75). Similar 

 discordant results could be quoted in other forms 

 including the guinea pig, rabljit and dog. In 1950 it 

 was suggested (153) that a possible reason for the 

 discrepancies in these reports might lie in varying 

 amounts of regeneration of the hypophysial portal 

 vessels across the site of stalk section. To test this idea 

 Harris (153) cut the pituitary stalk by a temporal 

 approach in 53 female rats and found that the portal 

 vessels in the rat may regenerate rapidly across the 

 site of section and that the reproductive capacity of 

 the animals could be correlated with such vascular 

 regeneration. Creep & Barrnett (129) and Barrnett 

 & Creep (16) have studied the effects of pituitary 

 stalk section in male and female rats, but since the 

 parapharyngeal route was used to section the stalk 

 the final inicroscopic study of the region was com- 

 plicated by the presence of scar tissue and adherence 

 of the structures to the drill hole in the base of the 

 skull. Recent studies have been made in other forms 

 such as the duck, ferret and rabbit. Benoit & Assen- 

 macher, after a preliminary study of the anatomy and 

 blood supply of the duck pituitary (20), devised an 

 operative approach to the pituitary region which 

 allowed them to make a lesion in the anterior part of 

 the median eminence (eminentiotomie), to cut the por- 

 tal vessels of the pituitary stalk and place a plate of 

 sclera at the site of section (tractotomie) or to cut the 

 nerve fibers of the stalk {mischotomie). The former two 

 procedures were found to result in atrophic testes and 

 the last procedure to have no eflfect on the normal 

 development of the testes (9, 10, 21-23). These beauti- 

 ful experiments on the duck have made possible then 

 a differentiation between the importance of the nerv- 



