648 INTERNAL SECRETION 



It is not at present possible to deduce from such clinical and 

 experimental observations as those described any coherent 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 skeleton 

 is scarcely to be doubted! The fact that administration of the 

 dried gland substance to dogs causes an increased excretion of cal- 

 cium on a diet rich in calcium is a further indication of its influence 

 on the metabolism 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 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 (Herring). And it has been suggested that in virtue 

 of the action of the hormones (p. 398) in this secretion on the vas- 

 cular system in general, and on the renal cells and the renal circula- 

 tion 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. 



(Pineal Gland A-fextracts of the pineal gland injected into the circula- 

 tion have no effect other than that due to the inorganic constituents 

 of the calcareous concretions or 'brain sand/ which are its character- 

 istic feature!! Since in early life the organ has a glandular structure 

 which is later replaced by fibrous tissue, it has been supposed that it 

 may exercise some function in connection with growth. But so far 

 the physiology of the pineal body is practically a blank sheet. The 

 alleged influence of the invasion of the gland in young children by 

 pathological growths in accelerating the development of the skeleton 

 and reproductive organs, which has been supposed to indicate that it 

 normally exerts a restraining or regulative influence on this develop- 

 ment, is at present purely fanciful. 



f Kidney .4-The experiments of Bradford, which seemed to indicate 

 tnatlche kMney, in addition to its function as an excretory organ, plays 

 an important, and indeed indispensable, part in protein metabolism, 

 possibly by forming something of the nature of an internal secretion.! 

 have not been confirmed. He stated that, when the half or two-thirds/ 

 of one kidney and the whole of the other have been removed from a 

 dog by successive operations, death ensues, although the quantity both 

 of water and urea excreted by the fragment of renal substance that 

 remains is far above the normal. In spite of the increased elimination 

 of urea, that substance was said to accumulate in the tissues, showing 

 that the destruction of protein was increased a conclusion which 

 seemed to derive support from the wasting of the animal. It has since 

 been shown that an increased output of nitrogen is not of constant 

 occurrence, and only takes place under the same conditions as in 

 starvation (p. 593). As a matter of fact, the animals waste and die 



