Biology of Man 509 



about 3 ounces; insulin was extracted from pancreas by the Canadians, 

 Banting and Best, in 1922 and has been used successfully in the treat- 

 ment of sugar diabetes, which would otherwise be fatal because of the 

 accumulation of toxic materials and constant loss of weight. 



6. Testes. — Two ovoid bodies suspended in the scrotum; the seminif- 

 erous tubules produce sperm; the interstitial cells between the tubules 

 secrete the endocrine hormones; castration (removal of testes) results in 

 the lack of development of secondary sexual characters; such a man 

 (eunuch) has a hairless face, high-pitched voice, and a tendency to 

 obesity; castration is frequently used on domestic animals; it is doubtful 

 if the administration of testicular hormones is of benefit in attempts at 

 rejuvenation. 



7. Ovaries. — Two bean-shaped organs (1^ inches long) attached 

 to the abdominal cavity near the uterus; the outer layer of germinal 

 epithelium produces eggs which are placed in internal follicles; each 

 month one (or more) follicle with its egg fills with fluid, comes to the 

 surface, and ruptures, thus releasing the egg into the oviduct; if after 

 ovulation the egg unites with a sperm, fertilization results; the ruptured 

 follicle fills with yellowish cells which constitute the corpus luteum 

 (corpus, body; luteum, yellow) ; the latter is absorbed in two weeks if 

 fertilization did not occur, but it enlarges and remains throughout the 

 period of pregnancy. 



8. Placenta. — This organ attaches the developing embryo to the wall 

 of the uterus and supplies it with nourishment; during pregnancy a hor- 

 mone similar to the luteinizing hormone of the pituitary is produced, and 

 its presence in the urine can be used for testing early pregnancy when 

 injected into nonpregnant, female animals such as rabbits, rats, mice, 

 etc. 



9. Stomach. — Certain cells of the lining of the stomach secrete a hor- 

 mone which stimulates the stomach to form digestive enzymes. 



10. Duodenum (First Part of Small Intestine). — Certain cells produce 

 several kinds of endocrine hormones. 



1 1 . Thymus. — A fairly large gland of children in the upper part of 

 the chest which regresses after puberty; no specific hormone has been 

 isolated but it is thought to be associated with juvenile growth. 



12. Pineal (Epiphysis). — One small, cone-shaped body located be- 

 tween the cerebral hemispheres dorsal to the pituitary; no specific hor- 

 mone but it is thought to be associated with growth. 



