670 



INTERNAL SECRETION ENDOCRINE GLANDS 



An active substance which has been termed ' tethelin,'* because of its 

 influence on growth, has been separated from the anterior lobe. On 

 intravenous injection into rabbits, it causes a slight fall of blood pres- 

 sure and rto diuresis. Its effects are therefore quite different from those 



of the posterior lobe. Mixed with the food 



f * /I"! /\ ^ m * ce ' *t h as Deen found to exert a charac- 



'.' rJ / '* teristic influence upon their growth, retard- 



ing it at certain stages, and accelerating it 

 at other stages (Robertson) . 



It is not at present possible to deduce 

 from such clinical and experimental 

 observations as those described any co- 

 herent theory of the function of the 

 pituitary. That there is some connection 

 between the normal action of the gland, 

 and in particular of its Anterior lobe, and 

 the normal growth and nutrition of the 

 body, including the skeleton, is scarcely 

 to be doubted. The fact that administra- 

 tion of the dried gland substance to dogs 

 causes an increased excretion of calcium 

 on a diet rich in calcium is a further 

 indication of its influence on the meta- 

 bolism of bone (Malcolm). But so far 

 is the precise nature of this influence, if 

 it exists, from being fully understood, 

 that authorities of repute are still divided 

 on the question whether the symptoms 

 of acromegaly and gigantism are due to 

 atrophy or to hypertrophy of the active 



3o f 



Fig. 217. Action of Infundi- 

 bular Extract upon Virgin 

 Uterus of Guinea- Pig. The 

 same dose was applied three 

 times in succession to an iso- 

 lated segment, at the points 

 marked by the arrows at 

 the bottom of the curves. 

 After each application the 

 segment was washed with 

 Ringer's solution at R. The 

 tracings have been made to 

 overlap. (Reduced to one- 

 half.) (Dale.) 



elements of the gland, to loss of its internal secretion, or to its 

 manufacture in excessive amount. There is evidence that the 

 colloid secretion of the posterior lobe, probably formed by the 

 epithelial cells of the pars intermedia, passes through the nervous 

 portion to enter the infundibulum and the third ventricle of the brain, 

 where it breaks down in the cerebro-spinal fluid (Hering). And 

 it has been suggested that in virtue of the action of the hormones 

 (p. 404) in this secretion on the vascular system in general, and on 

 the renal cells and the renal circulation in particular, the posterior 

 lobe constitutes a mechanism for the control of the secretion of urine. 

 But this suggestion is still in the realm of hypothesis. Some support 

 is given to it by the observation that continued irritation of the 

 posterior lobe by a plug of the gutta-percha compound used by 

 dentists for temporarily filling teeth introduced through the floer 

 of the sella turcica caused permanent polyuria in dogs, analogous 

 to the diabetes insipidus seen in man (Matthews). 

 * From T0/;Xu>s, growing, nourishing. 



