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HUMAN PHYSIOLOGY 



As there may be too much of the thyroid product, so 

 there may in other individuals be too little. The effects 

 are consistent with those that have been described. 

 Instead of nervousness there is apathy and dullness; 

 instead of emaciation there is corpulence. A peculiar 

 characteristic of the person with insufficient thyroid is 

 the overgrowth of the connective tissue beneath the 

 skin. This destroys the grace of all the contours and 

 particularly affects the features, making them heavy 

 and uncouth. The disease is called myxedema. 



The symptoms we have just re- 

 ferred to are those shown by a person 

 who has formerly had a normal thy- 

 roid but has lost its support more or 

 less completely. Another possibility 

 is that the thyroid may be inactive 

 from birth. This has a shocking con- 

 sequence: the child remains in a state 

 of arrested development both phys- 

 ically and mentally. It is said to 

 be a cretin. It is not only dwarfed 

 but ill-proportioned, having a heavy 

 head and abdomen and weak muscles, 

 thy- The development of a cretin can be 

 greatly assisted by adding to its food 

 at an early period some of the dried 

 substance of the thyroids of animals. The impulse given 

 to growth and the approximation to a normal type under 

 the influence of thyroid feeding are among the most 

 wonderful demonstrations of modern medicine. 



The main mass of the thyroid is composed of a tissue 

 which suggests that of a gland, such as the pancreas, 

 but with an important difference. The cells are ob- 

 served to surround recesses, as in the true gland, and the 

 recesses seem to be distended with a secretion, but there 

 are no ducts. Any active product must leave the seat 

 of its formation by the lymph or the blood. The force 

 of the term internal secretion comes home to one while 



FIG. 70. The 

 roid in its relation 

 the trachea. 



to 



