102 



THE VERTEBRATE ANIMAL: METABOLISM 



medical achievement. As is the case with all endocrine injections, 

 the dosage must be continued as long as results are desired. 



In the case of the gonads, or sex organs, there is evidence of the 

 production of endocrine secretions by both ovaries and testes. 

 These secretions are responsible for the control of the secondary 

 sex characteristics, but as yet there is too much confusion for 

 assignment of definite functions. Although the effect of other 

 endocrine secretions in association with those of the gonads is 



Fig. 59. — Section through pancreas showing an island of Langerhans sur- 

 rounded by acini. 



A, pancreatic acinus, the cells of which secrete pancreatic juice; C, blood capillary 

 which carries the secretion of the cells of the island; 1, cells of the island of Langerhans 

 which secrete insulin; L, lumen of acinus by way of which pancreatic juice passes to the 

 pancreatic duct. 



estabHshed, the exact relationships are still to be solved. The 

 confusion in data makes it impossible to draw definite conclusions. 

 From this brief sketch, in which some of the glands have been 

 treated individually, the student should not get the impression 

 that each member of the endocrine system acts alone. In cases of 

 " imbalance " a number of glands are always concerned, possibly 

 the entire chain. It is well to remember that the examples 

 given are the result of serious divergence from the nonnal. A 

 vast series of deviations from the typical human reactions seem 



