196 



DUCTLESS GLANDS 



The parathyroid. There are four small structures attached to 

 the thyroid glands, and weighing in all about two grains. They are 

 the parathyroids (para means "near"). These, also, produce an 

 internal secretion which is related to the calcium metabolism. 

 Their removal, or atrophy, gives rise to tetany, a sudden convul- 

 sive contraction of the muscles, which may result in death. 

 The injection of small doses of parathyroid extract usually results 

 in temporary relief. The effects of too great activity of the 



parathyroids have not 

 been fully ascertained, al- 

 though it has been shown 

 by Collip that the injection 

 of parathyroid extract into 

 the blood of an animal will 

 increase the calcium con- 

 tent of the blood while the 

 removal of a part of the 

 parathyroid tissue will give 

 rise to a calcium deficiencv. 

 Pituitary gland. The 

 pituitar}^ gland weighs 

 about one sixteenth of an 

 ounce and is located at the 

 base of the skull. Galen 

 and Vesalius knew that 

 there w^as a pituitary gland. 

 They thought it had some- 

 thing to do with the 

 secretion of the nose. 

 (Pituitary is from the 

 Latin word jntuita, meaning phlegm.) Modern experimentation 

 has proved that there is no such connection or relationship. 

 There seems to be sufficient evidence to justify the acceptance of 



Juunial of Heredity 



Giantism and dwarfism are probably due to defective 

 pituitary glands. 



