ACTIVATORS, KINASES AND HORMONES 191 



responsible for certain well-known correlations of function : 

 The pancreatic secretin formed in the epithelium of the 

 duodenum or jejunum which stimulates the flow of pan- 

 creatic secretion; the gastric secretin formed iu the pyloric 

 mucous membrane which gives rise to the chemical secretion 

 of gastric juice ; a secretin formed in the duodenal epithe- 

 lium which stimulates the formation of intestinal juice in 

 the following segments of the intestin ; unknown hormones 

 of pancreatic origin which determine the absorption activ- 

 ity of the intestinal epithelium; vaso-dilator hormones 

 formed in tissues in functional activity and which have a 

 specific effect upon the vessels of the functioning organ; 

 a vaso-constricting and a diuretic hormone formed in the 

 posterior lobe of the pituitary body ; a hormone controlling 

 the growth of the bones and connective tissues produced in 

 the anterior lobe of the pituitary body ; a hormone control- 

 ling the oxidation of sugar in the body and produced in 

 the cells of the islands of Langerhans in the pancreas; a 

 hormone produced in the thymus which controls possibly in 

 some way the development of the reproductive organs; a 

 vaso-constricting hormone formed in the kidneys; a hor- 

 mone in the salivary glands which controls the flow of 

 water from the blood capillaries in the glands; a hormone 

 produced in the foetus in utero which stimulates the growth 

 of the mammary glands; a hormone in the ovary which 

 controls the growth of the uterus and the processes of 

 menstruation; a hormone in the ovary which controls the 

 implantation of the fertilized ovum and the growth of 

 placental tissue ; a hormone in the testis which initiates the 

 development of the secondary sexual characteristics in the 

 male; hormones of an indefinite number, produced in all 

 the tissues and acting specifically upon the determinants 

 in the gametes in such a way as to make possible theitrans- 

 mission of acquired characteristics. It is evident from this 

 summary that there is a well-developed tendency in 

 physiology at the present day to utilize the conception of 

 hormones to explain all relationships not otherwise intel- 



