ACTIVE PRINCIPLES OF PARS NEURALIS 



ampoules, solutions of the active principles at pH 3-4, if kept 

 in the icebox, retain their activity without loss for at least a 

 year (Smith and McClosky, 1924). The heat stability of 

 aqueous extracts at one or different pH's has been studied by 

 Smith and McClosky (1924), Gerlough (1930), Gerlough and 

 Bates (1930), and Guha and Chakravorty (1933). The effects 

 of digestion by different enzymes have been studied by Dale 

 and Dudley (1921), Rees and Whitehead (1923), Thorpe 

 (1926), and GuUand and Macrae (three papers, 1933). 



IS THERE CONVINCING EVIDENCE THAT THE 



PARS NEURALIS IS A GLAND OF 



INTERNAL SECRETION ?5 



Evidence bearing on this question has been briefly dis- 

 cussed already (chap. ii). It is proposed here to consider in 

 greater detail the numerous data which support or deny the 

 belief that the pars neuralis (perhaps in association with the 

 pars intermedia) is an internally secreting gland of some im- 

 portance. The simplest argument in favor of an affirmative 

 answer to the question proposed above is deductive: sub- 

 stances having powerful effects on the movements of the 

 uterus, on the blood pressure, and on the secretion of the 

 urine can be extracted from the pars neuralis; therefore, in 

 life these substances are secreted and produce, in a less exag- 

 gerated fashion, their characteristic effects. This argument, 

 however, does not attempt to explain why the posterior lobe 

 of the male animal contains just as much oxytocic principle 

 as the female posterior lobe; it also leaves out of account the 

 function of the oxytocic hormone in female animals of lower 

 classes which possess no uterus. 



The evidence furnished by studies of hypophysectomized 

 animals. — Hypophysectomy is probably never complete; the 

 most important tissue remaining is a large part of the pars 



5 For a discussion of the possible origin and paths of secretion of the active prin- 

 ciples of the pars neuralis, see chap. i. 



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