PANCREAS 535 



. Thyroid gland is used in myxoedcema, goitre, obesity, and 

 other cases in which a deficient production of the secretion is 

 indicated. 



Note. Parathyroid glands are small, four in number and lie close to or 

 embedded in the thyroid. Their removal induces tetany, and certain forms 

 of tetany are benefited by the use of preparations of the parathyroids. 



The pituitary body, a gland situated at the base of the brain, forms one or 

 more secretions of great physiological importance. It consists of a posterior, 

 an intermediate and an anterior portion. Preparations of the posterior and 

 intermediate portions, of the anterior portion and of the whole gland are 

 employed medicinally. Extracts of the posterior and intermediate portions 

 injected hypodermically raise the blood pressure and promote contraction of 

 the uterus ; the anterior lobe, dried and powdered, influences growth and 

 development. From neither portion has an active constituent been isolated. 



The spleen is a solid organ enclosed in a capsule. Its functions are not 

 fully known, but it appears to be concerned with the protection of the body 

 against disease by removing micro-organisms from the blood. 



The thymus, or throat-bread, is composed of lobules united by connective 

 tissues. Its secretion has a marked influence on sexual development. 



GLAND WITH DUCT 



PANCREAS 



(Pancreas) 



Source, &c. The pancreas used in medicine is obtained from the 

 pig, Sus scrofa, Linrie (N.O. Ungulata). 



Description. The pancreas is a gland, weighing (in man) from 60 

 to 100 grammes, situated near the stomach in a depression formed by 

 the duodenum to which it is closely attached, and into which it dis- 

 charges its secretion, the pancreatic juice, by means of a principal 

 branching excretory duct called the pancreatic duct. Immediately 

 after the introduction of food into the stomach, the pancreas begins 

 to produce its secretion, which in the case of man averages about 150 

 grammes a day. The epithelial cells of the small intestine produce 

 a substance termed prosecretin which, when acted upon by dilute 

 hydrochloric acid, yields a hormone, secretin ; this passes into the 

 blood and causes the stimulation of the pancreas. The pancreatic 

 juice contains xanthine, guanine, leucine, sodium carbonate and other 

 substances, together with the zymogens of four enzymes, but not 

 the enzymes themselves, these being liberated from the zymogens 

 by means of the enzyme, enterokinase, which is present in the duo- 

 denum. 



