10 THE ROYAL SOCIETY OF CANADA 



body, to cite one of the best known examples, are in some respects 

 antagonistic. lodothyrin, the active principal in the thj-roid dilates 

 blood vessels, increases the rapidity of the heart, and lowers blood 

 pressure, as we see in the disease known as exophthalmic goitre. Ex- 

 tract of the infundibulum of the pituitary slows the pulse and raises 

 blood pressure. Deficient thyroid secretion, as in cretinism, causes 

 lack of development of the skeleton and soft tissues, as well as di- 

 minished function. Excess of the internal secretion of the anterior 

 portion of the pituitary produces gigantism in the young and acro- 

 megaly in the mature. Other notable instances might be mentioned 

 in connection with other organs. 



Certain of these glands of internal secretion have a remarkable 

 influence over growth and metabolism. Disease of the pituitary body, 

 and of the adrenal cortex; removal of the testes or ovaries, tend to 

 produce obesity. The thyroid, the parathyroids, and the ovaries, 

 seem to stimulate the excretion of calcium salts. The inter-relation- 

 ships of these various glands are very intricate, but are gradually being 

 unravelled. One of the most remarkable and interesting developments 

 of modern investigation is the discovery that organs and tissues may 

 influence one another chemically from a distance. Bayliss and Starling 

 were able to isolate from the cells of the duodenum and upper portion 

 of the jejunum a substance, which they called secretin, that had the 

 striking property, when injected into the circulation, of stimulating 

 the flow of the pancreatic juice. This substance was purely chemical 

 in nature, as it was soluble in alcohol and was not destroyed by heat. 

 To this class of substance, on account of their property of stimulating 

 secretion, they gave the name "Hormone" (Greek, hormao, I excite). 

 Wertheimer further discovered that the acid contents of the stomach 

 acted as a hormone to excite the production of secretin. A singular 

 thing, however, was that the pancreatic secretion so produced was de- 

 ficient in trypsin. But, it was later found that the succus entericus 

 elaborated a substance, called enterokinase, which had the power of 

 converting the precursor of trypsin, trypsinogen, into trypsin, and so 

 the chain is made complete. Other hormones have been discovered, 

 and no doubt, when we consider the complexity of vital processes, their 

 number must be legion. The pyloric glands of the stomach secrete a 

 hormone which excites the production of HCl from the glands at the 

 cardiac end. The pancreas supplies a hormone which converts carbo- 

 hydrates in liver and muscle into glycogen. The pituitary manufac- 

 tures a hormone that stimulates the growth of bone. The corpus lut- 

 eum of pregnancy produces a substance that causes the development 

 of the maternal decidua. The foetal tissues contain a hormone that 

 causes proliferation of the mammary gland and the secretion of milk. 



