Glands 115 



slowly; growth, except of connective tissue, stops; and death may follow. 

 In children, atrophy of the thyroid gland produces the state of arrested 

 development known as cretinism. Cases of cretinism and myxedema may 

 be relieved by feeding the patient fresh or dried thyroid glands of animals. 

 The hypertrophy, or excessive growth of the thyroid (one form of goiter), 

 is productive of nervous irritability and muscular weakness. The function 

 of the parathyroids is somewhat in dispute. In the view of some experi- 

 menters they are similar in nature to the thyroid, and if the latter be re- 

 moved without injuring the former they can to a certain extent fulfill the 

 the latter's function. This theory is probably wrong. 



The pituitary body consists of two lobes, anterior and posterior (the 

 hypophysis and the infundibulum) , 2i with a pars intermedia between. 

 The posterior lobe seems to have no secretory function. The secretion 

 of the anterior lobe seems to promote growth, especially of the bones and 

 connective tissue. The condition known as acromegaly or gigantism, in 

 which the bodily frame grows to excessive size, are thought to be due to 

 over-development or over-activity of this lobe. The secretion of the pars 

 intermedia has an exciting effect on smooth muscle and on the gland-cells 

 of the kidneys. Removal of the entire pituitary body causes death. 



Of the functions of the other ductless glands little is known. The 

 thymus, which enlarges during the first two years of life and then di- 

 minishes so that at puberty it is insignificant, probably has a specific influ- 

 ence on the growth of the child. The pineal body is glandular only 

 during childhood, becoming a mere fibrous body at adolescence. Its secre- 

 tion probably retards the development of the body, especially the develop- 

 ment of the reproductive organs. The secretion of the adrenal glands 

 (adrenalin, suprarenalin or epinephrin) has a marked effect on smooth 

 muscle and gland cells, producing the same activity in these organs as is 

 produced by stimulating the nerve supplying them. Removal of the ad- 

 renal bodies always causes death in from twelve to twenty-four hours. 



Cannon has shown that the secretion of adrenalin is increased in ani- 

 mals under the influence of stimulations producing such emotions as fear 

 or rage. The importance of the secretion in such circumstances can readily 

 be understood, since it acts as a stimulant to the muscles and other organs 

 and in particular increases the liberation of glycogen from the liver into 

 the blood, and thus increases the energy-supply to the muscles. The effect 

 of adrenalin on the digestive process is marked. It checks both the secre- 



s *The 'anterior' lobe really lies behind the 'posterior' lobe in the human animal. 

 The terms ' anterior ' and ' posterior ' refer to the origin of the lobes. See first para- 

 graph of Chap. VI. 



