THE PITUITARY BODY 



making extracts (alcoholic extracts of plasma) may not have 

 been suitable for the pituitary vasopressor principle. 



The oxytocic prhiciple. — The additions to our knowledge of 

 the possible physiological importance of the oxytocic princi- 

 ple in parturition are, for the most part, only of inferential 

 value. Newton (1937) found that the isolated cervix uteri 

 of the rat and guinea pig, in any stage of sexual activity in- 

 cluding pregnancy, is very insensitive toward the oxytocic 

 principle (concentration of 40 units per liter of bath-fluid). 

 Newton considers that this fact strengthens the evidence 

 favoring the importance of oxytocic-principle secretion in 

 normal parturition. Possibly important interrelationships 

 between the secretion of oestrogens or progesterone and the 

 action of the oxytocic principle are discussed on pages 261-62. 

 According to Ingram and Fisher (1937), if diabetes insipidus 

 is produced in pregnant cats by a lesion of the supraoptico- 

 hypophysial system, the subsequent parturition is incom- 

 plete and terminates in death. However, others (including 

 Houssay, 1935, and Robson, 1936-37) have demonstrated 

 that normal parturition can take place in the cat, dog, mouse, 

 rabbit, and rat after the removal of the posterior lobe or after 

 hypophysectomy. This fact must be taken into account if 

 the initiation or continuation of labor is to be explained as 

 the result of oestrogen-sensitization of the uterus toward the 

 oxytocic principle or if the interference with parturition ob- 

 served by Ingram and Fisher is to be ascribed to a deficiency 

 in the secretion of the oxytocic principle. 



The pars nenralis and menstruatio?2. — Hartman and Firor 

 (1935) have again suggested that menstruation possibly re- 

 quires a functioning pars neuralis. However, the evidence 

 offered does little to commend this hypothesis: of four im- 

 mature monkeys in which complete hypophysectomy was at- 

 tempted, the operation was successful in only one; "oestrin- 

 deprivation" bleeding after 640 rat-units of oestrin was ob- 

 served in all the animals except the one completely hy- 

 pophysectomized. In the experiments of Smith, Tyndale, and 



[290] 



