NERVOUS AND ENDOCRINE CONTROL 1 45 



single case of congenital goiter was found during three years of observa- 

 tion. It is an interesting fact that, 1,500 years before Christ, the Chinese 

 used iodized salt in the form of burnt seaweed or burnt sponge for the 

 treatment of goiter. 



Frog or salamander tadpoles fed on thyroid are forced into precocious 

 maturity. Frog tadpoles quickly develop legs, absorb their tails, and trans- 

 form into miniature frogs, sometimes no larger than a fly. On the other 

 hand, a young tadpole deprived of its thyroid glands is unable to become 

 a frog though it continues to live, and may grow far beyond the normal 

 size of a tadpole. If at any time such a tadpole is fed thyroid, however, it 

 promptly undergoes metamorphosis. 



It is perhaps a significant fact, according to Hoskins and Sleeper, that 

 more than 10 per cent, of the victims of the psychosis commonly called 

 dementia praecox — a malady that fills one-fifth of all occupied hospital 

 beds in the country — show some degree of thyroid deficiency, and gen- 

 erally improve after administration of thyroxin. 



To discover if too much or too little thyroxin is present in an individual, 

 a test called the "basal metabolism test" is employed. A normal resting 

 person who has had no food for twelve hours produces a remarkably 

 constant amount of energy in a given time as shown by the even carbon 

 dioxide output which results from internal oxidation. In persons suffering 

 from goiter or from lack of thyroid activity, the severity of the condition 

 can be estimated by determining how far the rate of internal oxidation de- 

 viates from that of a normal individual. 



The parathyroids in man usually exist as four minute glands weighing 

 in all not over two grains, although additional accessory parathyroid tissue 

 is not uncommon. Each is about the size of a small pea. They are closely 

 attached to the thyroid. Their secretion shares with Vitamin D, control 

 of the calcium and phosphorus content of the blood, and since calcium is 

 of prime importance in many physiological processes from clotting of 

 blood and muscular tone to formation of bones and teeth, and phosphorus 

 is likevv'ise indispensable, the proper functioning of these glands is all- 

 important to the organism. Parathyroid deficiency is characterized by 

 overexcitability of the whole nervous system, and often by epileptic-like 

 seizures; fractured bones are delayed in healing, and in the young, growth 

 of the skeleton is retarded. Complete removal brings about a condition 

 known as "tetany," characterized by painful spasmodic contractions of 

 the muscles of the extremities. The calcium content of the blood is greatly 

 diminished. The respiratory tract, the temperature of the body and the 

 heart are also affected. Injection of a soluble calcium salt will relieve the 

 attack of tetany and, for a time, restore the individual to normal. Death 

 results in a few days after the removal of the glands if the condition re- 

 mains untreated. 



The pituitary gland is a small body of double origin, attached by a 



