240 NUTRITIONAL PHYSIOLOGY 



functioning of the thyroid. Very recently it has been 

 shown that what has been called the thyroid is, in reality, 

 a compound structure. In addition to the type of tissue 

 which forms the main mass of the organ in man, there are 

 four nodules of a different sort, the parathyroids. These 

 undoubtedly have a chemistry of their own and a distinc- 

 tive relation to the economy of the body. For a statement 

 of their peculiar importance reference must be had to 

 larger works on physiology. 



The full measure of the influence which radiates from 

 the thyroid can be appreciated by considering the condi- 

 tion known as cretinism. This is the term used to de- 

 scribe the state of individuals in whom the thyroid has 

 never performed its proper work. These subjects remain 

 for years in a condition of arrested progress, both physical 

 and mental. They are uncouth dwarfs with large heads, 

 slack-walled abdomens, and feeble limbs. If they survive 

 to the age of twenty or thirty they will scarcely have ad- 

 vanced beyond the stage reached at four or five. That 

 the lack of the thyroid is actually responsible for these 

 shocking cases is now abundantly proved. The demonstra- 

 tion is found in the happy circumstance that great im- 

 provement follows the judicious feeding of thyroid prepa- 

 rations to cretins. The material is obtained from calves 

 or sheep. Its administration for a few months often re- 

 sults in transforming a repulsive cretin into a presentable 

 child with a prospect of at least a moderate mental de- 

 velopment. 



In the dog it is possible to graft an extra thyroid into 

 the abdominal cavity and then to remove the original 

 gland, when the second organ will assume the functions 

 necessary to the preservation of health. This was an 

 important discovery, since it removed the ground for a 

 prevalent opinion that the service of the thyroid was 

 limited to the reflexes which it was supposed to originate. 

 It had been thought that the gland affected the nutrition 

 and general health by sending impulses along the nerves 

 leading from it to the centers. A gland substituted for the 



