508 Animal Biology 



3. Parathyroids. — Usually four small compact masses of cells closely 

 associated with the thyroid but which differ from the latter structurally 

 and functionally. 



4. Adrenals (Suprarenals). — One soft, cup-shaped gland covering the 

 upper part of each kidney; composed of an outer, pale pink cortex and 

 a dark inner medulla, which differ as to embryologic origin, structure, 

 and functions; the two parts are separate in certain lower vertebrates. 



Fig. 253. — Cretin, 19 years of age, showing dwarfism, deficient bone develop- 

 ment, thickened lips, thick pasty skin, etc. (From Bard: Macleod's Physiology 

 in Modern Medicine, The C. V. Mosby Co.) 



5. Pancreas. — This organ secretes digestive juices which are carried 

 away by ducts, but certain clusters of cells (islands of Langerhans) are 

 without a duct and secrete endocrine hormones; it is flat and irregular 

 and lies in the curvature between the stomach and duodenum; weighs 



