ENDOCRINE GLANDS AND THEIR FUNCTIONS 205 



effective as androsterone in bringing about regeneration of acces- 

 sory sex organs in castl-ated males. Recently androgenic hormones, 

 which are potent enough to affect the growth of comb in the capon, 

 have been found in the urine and ovaries of female animals. 



Theelin (oestrin, estrogen, folliculin, menoform, progynon) has 

 been isolated from liquor folliculi, pregnancy urine, the placenta, 

 and amniotic fluid. This substance causes (1) increased growth of 

 the accessory female organs (uterus, oviducts, etc.), including changes 

 in the glands of their linings and in vascularization; (2) contraction 

 of the smooth muscle of the uterus; (3) initial growth of mammary 

 glands and nipples; and (4) sudden lowering of theelin concentra- 

 tion in blood (suggested as cause for bleeding during menses). The 

 secretion of theelin is influenced by the gonadrotropic principle of 

 the anterior pituitary. 



Progesterone (lutein hormone, corporin, luteosterone progestin) is 

 a female hormone produced by the corpus luteum, the yellow body 

 of material which forms in the ruptured Graafian follicle after the 

 escape of the ovum. It produces the following effects: (1) sensitiza- 

 tion of the lining of the uterus so that implantation or attachment 

 of the zygote may take place in case of fertilization; (2) develop- 

 ment of placenta ; (3) arrest of rhythmic contractions of the smooth 

 muscle of the uterus; (4) inhibition of ovum production and uterine 

 bleeding. 



The influence of other hormones of the body is noted in the repro- 

 ductive and sexual processes. The effect of the pituitary has already 

 been mentioned. The thyroid secretion probably plays a role, not 

 clearly understood, in the female reproductive processes, since the 

 thyroid always enlarges at puberty and during pregnancy. Another 

 hormone is thought by some investigators to be formed in the pla- 

 centa during the development of an embryo. The interrelationships 

 of these hormones are involved, and doubt exists in some cases as 

 to their exact functions. 



The Pancreas 



This is one of the organs serving a dual purpose in the body; it 

 secretes from a group of its cells, called the islands of Langerhans, a 

 hormone designated as insulin. Experiments have shown the action 

 of insulin to be concerned with the metabolism of carbohydrates 

 and fats. Its presence facilitates the combustion of carbohydrates, 



