REGULATORS 601 



A physiological hypertrophy occurs in pregnancy, during 

 which the ovarian functions are in abeyance, the chief cells 

 being increased. In the male, removal of the testes leads to 

 hypertrophy of the pituitary. 



While the pituitary thus exercises a stimulating action on 

 the growth of the connective tissues and of the gonads, the 

 latter appear to have a checking action on the pituitary. 

 More work upon this is required. 



III. From the Intestine. 

 5. Pancreas. 



The development and structure of the pancreas have been 

 described (p. 300). 



The effects of removal in producing the condition of diabetes 

 have been considered (p. 357), and it has been shown that the 

 organ produces an internal secretion which checks the mobilisa- 

 tion of sugar in the liver, and possibly facilitates its utilisation 

 by the muscles. The transplantation of a piece of pancreas 

 prevents the onset of these symptoms, but the administration 

 of pancreas or of extracts of the pancreas does not do so. 



The internal secretion of the pancreas acts in the opposite 

 direction to that of the chromaffin tissue and the thyreoid. 

 The fact that, after removal of the pancreas, adrenalin causes 

 dilatation of the pupil seems to indicate that its internal 

 secretion inhibits the action of the termination of the true 

 sympathetic in the iris, and therefore probably also in the 

 liver. 



It is probably the islets of Langerhans which yield the 

 active principle. The true islets are developed early in foetal 

 life from the epithelium of the ducts. A case has been 

 described in which excision of a piece of pancreas, which had 

 been left after partial removal of the organ, led to glycosuria, 

 and in which the fragment was found to have degenerated and 

 to be composed entirely of islet tissue. 



6. The Mucous Membrane of the Small Intestine. 

 The production of secretin and its action on the pancreas 

 have been dealt with on p. 321. 



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