Chap. XVI] 



DUCTLESS GLANDS 



315 



and puffy. The mental faculties become blunted and idiocy re- 

 sults unless proper treatment is instituted. 



Cretinism and myxoedema are both supposed to be due to a lack 

 of the internal secretion of the thyroid, and much success has 

 followed the administration of thyroid extract in various ways. 



Goitre is a condition in which the gland is enlarged, but the se- 

 cretion may not be interfered with. 



Exophthalmic goitre is a disease characterized by extreme ner- 

 vousness, quickened heart action, protruding eyeballs, and goitre. 

 It is caused by an overabundant production of thyroid secretion, 

 due to enlargement and over acti^-it^' of the dand. 



Fig. 164. — The Thymus, the Sternal and Costal Cartilages having been 

 Removed. (Gerrish.) 



(2) The Parathyroids. — Embedded in the surface of each 

 lateral lobe of the thyroid are two little masses, each about one- 

 fourth inch (6.25 mm.) in diameter. They are solid accumula- 

 tions of epithelioid cells, invested with a tunic of areolar tissue 

 and well supplied with blood-vessels. The function of the para- 

 thyroids is supposed to consist in neutralizing toxic substances 

 found elsewhere in the body. 



(3) The Thymus. — The thymus consists of two large masses 

 of glandular tissue situated below the thyroid and in front of the 



