ACTIVE PRINCIPLES OF PARS NEURALIS 



removal of the pars neuralis (Braun-Menendez, 1932). Hypo- 

 physectomized dogs may metabolize water like normal dogs 

 (Houssay and Hug, 1921, and others). 



Despite all that has been written on the presumed im- 

 portance of the oxytocic hormone in parturition, there is 

 good experimental evidence that normal parturition can 

 occur in the dog, cat, and rabbit after hypophysectomy or 

 after the removal of the posterior lobe (Aschner, 191 2; Dott, 

 1923; Allan and Wiles, 1932; Firor, 1933) and in the mouse 

 and rat after the removal of the posterior lobe or the whole 

 pituitary (Smith, 1930; Selye, Collip, and Thomson, 1933- 

 34). In Smith's carefully controlled experiments the whole of 

 the pars neuralis and the pars intermedia was removed. Sub- 

 sequently, pregnancy, parturition, and lactation occurred 

 exactly as in normal animals. Whether or not, as some be- 

 lieve, hormones identical with or similar to those of the pars 

 neuralis are produced vicariously by the pars tuberalis and 

 the tuber cinereum cannot be decided from the available 

 data. Earlier reports (e.g., Trendelenburg, 1924; Miura, 

 1925) indicated that the oxytocic substance of cerebrospinal 

 fluid disappeared after hypophysectomy. Later work, how- 

 ever, seemed to show that hypophysectomy merely lowered 

 the concentration of the substance and then only temporarily 

 (Geesink and Koster, 1928; Sato, 1928; Trendelenburg, 1928; 

 Trendelenburg and Sato, 1928).*' Trendelenburg and Sato 

 concluded that vicarious production of the active principles 

 of the pars neuralis took place in the tuber cinereum. After 

 hypophysectomy the tuber cinereum was found to contain 

 increased amounts of oxytocic and antidiuretic (including 

 "chloride-concentrating") substances. (See also the com- 

 ments in chap, ii.) 



Verney's acute experiments (1926) have been discussed 

 already (pp. 74-75). According to Verney, blood which has 



* See also McLean's account (1928) of changes or lack of changes in the concen- 

 tration of oxytocic substance in the blood of hypophysectomized dogs. 



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