PARS NEURALIS AND INTERNAL SECRETION 



no water was destroyed in strong solutions of acid or alls:ali, 

 as is that in an extract of the pars neuralis. The conclusions 

 of Oilman and Goodman from these experiments seem logical. 

 The amount of vasopressor or diuresis-inhibiting principle se- 

 creted by the pars neuralis fluctuates with the body's need 

 for water conservation. Normally, the amount secreted is 

 so small that none can be detected in the glomerular filtrate. 

 If there is a shortage of water, its retention in the body is 

 largely due to a reduction in the volume of urine secreted. 

 And the emergency secretion of an increased amount of 

 diuresis-inhibiting hormone by the pars neuralis is perhaps 

 the important means of accomplishing this by increasing the 

 reabsorption of water in the renal tubules. The unusual 

 amount of hormone secreted filters in part through the glo- 

 meruli and can then be detected in the urine. 



2. The importance of hypothalamic nuclei^ especially the 

 supraoptic nuclei^ for maintaining the secretion of the vasopres- 

 sor principle. — In several recent reports of experiments in cats 

 and monkeys, Fisher, Ingram, and Ranson^ have shown that 

 the supraoptic nuclei of the hypothalamus may be essential 

 not only to liberate suitable amounts of vasopressor hormone 

 — to prevent undue loss of water by way of the kidneys — 

 but also to maintain the pars neuralis anatomically. Cats 

 were used for most of their experiments. Employing the 

 Horsely-Clarke stereotaxic instrument as a means of placing 

 lesions in difi-'erent parts of the hypothalamus, they produced 

 a severe permanent diabetes insipidus in a number of cats.^ 

 Later, sometimes after months of severe diabetes insipidus, 

 the animals were killed, and the hypothalamus and pituitary 



■* Fisher, Ingram, Hare, and Ranson (1935), Fisher, Ingram, and Ranson (1935), 

 Fisher and Ingram (1936), Ingram and Fisher (1936), Ingram, Fisher, and Ranson 

 (1936). 



s The diabeces insipidus appeared about 8-12 days after a suitable lesion(s) had 

 been made. Polyuria appeared to precede polydipsia (see also Fisher, Magoun, and 

 Hetherington, 1938). In addition, a transient polydipsia and polyuria were com- 

 monly observed immediately after operation. These initial transient changes have 

 been observed by a number of authors using different animals. Usually they are 

 attributed to an effect on the nervous system alone. 



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