THE PITUITARY BODY 



units, and 5.0-8.1 units, respectively. The concentration of 

 hormone (pressor) was about the same in the posterior lobe 

 of the ox and the rabbit, but was considerably higher in the 

 posterior lobe of other animals. 



In the cat as in the rat thyroid-feeding or thyroidectomy 

 does not affect the amount of posterior-lobe principles 

 (Herring, 1921). Castration (of the toad) or ovariectomy 

 (guinea pig) probably does not affect the amount of the 

 oxytocic hormone in the pituitary (Siegert, 1929; Novelli, 

 1932). According to Jores and von Wittern (1934), a marked 

 increase in the amount of oxytocic principle is found late in 

 pregnancy in the rabbit. Their conclusions are based on 

 studies in only a few animals; moreover, their estimate of the 

 total amount of oxytocic principle in the pituitary of the non- 

 pregnant rabbit (0.05-0.25 unit) is inexplicably lower than 

 that of Simon and Kardos (0.6-1.5 units). Smith and Mc- 

 Closky (1923) concluded that the concentration of oxytocic 

 principle in the posterior lobe of the ox is the same in both 

 male and female animals as well as after gonadectomy; simi- 

 larly, the concentration of the hormone is not different at 

 different times of the year. The potency of the human pars 

 neuralis has been investigated by Lampe (1926), Jores and 

 Zschimmer (1934), and Simon and Nagy (1934). Differences 

 related to sex were not observed. The concentration of hor- 

 mone may be highest in the infant; the total amount (maxi- 

 mum, 30 units) appeared to be greatest in the age-period 

 18-50 years (Simon and Nagy; Jores and Zschimmer believed 

 the maximum occurred in the seventh decade). The condi- 

 tions necessarily were not uniform (5.5-82 hours post- 

 mortem); the total amounts of hormone found varied greatly. 



THE ASSAY OF THE ACTIVE PRINCIPLES 



The oxytocic principle. — Following the discovery of Dale, 

 Bell and Hicks, and others (1909) that extracts of the pars 

 neuralis cause a powerful contraction of the smooth muscu- 



[322] 



