PARS NEURALIS AND INTERNAL SECRETION 



and compared his results with the findings of others. Von 

 Hann conckided that diabetes insipidus in man can occur 

 only if (i) the pars neuralis is destroyed or severely damaged, 

 (2) the pars glandularis is functionally active, and (3) there 

 is no serious disorder of the heart and kidneys. Richter 

 (1934) also maintained that diabetes insipidus in rats is read- 

 ily produced, if all the posterior lobe but only part of the 

 anterior lobe is removed. The majority of the recent reports 

 support the von Hann-Richter hypothesis that typical dia- 

 betes insipidus requires the abolition of pars neuralis secre- 

 tion but the persistence of pars glandularis secretion. 



According to this hypothesis the development of diabetes 

 insipidus may proceed in the following way. Either by dis- 

 ease or by experiment the internal secretion(s) of the pars 

 neuralis no longer escapes into the blood or body-fluids. This 

 may be accomplished by interruption of the secretory fibers 

 from hypothalamic nuclei to the pars neuralis as by injury 

 to the nuclei or to the supraoptico-hypophysial tract in the 

 tuber cinereum or stalk, or by removal or destruction of the 

 pars neuralis itself. Abnormal depletion (polyuria) of the 

 body water then occurs, because the vasopressor hormone, 

 which by its effect on the loop of Henle normally insures an 

 adequate reabsorption of water during the secretion of urine, 

 no longer finds its way into the blood. Compensation is then 

 effected by the drinking of large amounts of water (poly- 

 dipsia). Why, then, is a normally secreting pars glandularis 

 also necessary for the maintenance of diabetes insipidus .'' 

 Presumably a normal rate of formation of glomerular filtrate 

 in the kidneys depends upon normal metabolic activity, 

 which in turn depends to an important extent on the glands 

 of internal secretion, particularly the thyroid. If the anterior 

 pituitary, without whose secretion the principal other endo- 

 crine glands become inactive, is also removed, metabolic ac- 

 tivity is reduced and probably abnormal. Consequently, a 

 marked reduction in the volume and rate of formation of 

 glomerular filtrate takes place, so that the lack of an adequate 



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