CHAPTER XXV 



THE DUCTLESS GLANDS 



THE ductless glands form a heterogeneous group of organs, most of 

 which are related in function or development with the circulatory 

 system. The function of a gland that has a duct is a comparatively 

 simple physiological problem, but the use of ductless glands was 

 for long a puzzle to investigators. Kecent research has, however, 

 shown that most of, if not all, the ductless glands do form a 

 secretion, and this internal secretion, as it is termed, leaves the 

 gland by the venous blood or lymph, and thus is distributed and 

 ministers to the needs of parts of the body elsewhere. Many of 

 the glands which possess ducts and form an external secretion, form 

 an internal secretion as well. Among these, the liver and pancreas 

 may be mentioned. The term internal secretion was first used by 

 Claude Bernard in relation to the liver. 



In many cases the internal secretion is essential for life, and 

 removal of the gland that forms it, leads to a condition of disease 

 culminating in death. In other cases the internal secretion is not 

 essential, or its place is taken by that formed in similar glands in 

 other parts of the body. 



The body is a complex machine ; each part of the machine has 

 its own work to do, but must work harmoniously with other parts. 

 Just as a watch will stop if any of its numerous wheels get broken, 

 so the metabolic cycle will become disarranged or cease altogether if 

 any of the links in the chain break down. 



In unravelling the part which the ductless glands play in this 

 cycle, it is at present impossible in many cases to state precisely 

 what the particular function of each is; all one can say is, when 

 the gland is removed or its function interfered with, that the meta- 

 bolic round is broken somehow, and that this upsets the rest of 

 the machinery of the body. The difficulty of investigating this 

 subject is increased by the fact that it is impossible to get the 

 internal secretion in a state of purity and examine it ; it is always 



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