MAMMALIA— PHYSIOLOGY 445 



Pancreas. — The digestive enzymes of the pancreas act on pro- 

 teins, carbohydrates and fats. The internal secretion,(^£^£r£^^ 

 successfully isolated by Banting^ and associates in 1922, was secured 

 from the Islands of Langerhans of the pancreas of fetal calves. 

 J. J. Abel has since then prepared pure crystalline i nsulin, so power- 

 ful that only i/ioo of a grain is the daily dosage for a diabetic. 

 Many lives are now saved annually by the use of " insulin." 



Endosecretory Glands without a Duct. Thyroid. — The thyroid 

 glands contain ten times as much iodin as any other organ in the 

 body. Iodin in food and water must be optimum, or goiter may 

 result. The thyroids stimulate carbohydrate and calcium metab- 

 olism and bear an important relation to body fats. Pioneer studies 

 by Gudernatsch with tadpoles indicated that if fed thyroid extract, 

 they metamorphosed rapidly into small toads. Uhlenhuth has 

 shown that anterior lobe substance from the pituitary gland will 

 stimulate the thyroid and induces precocious metamorphosis in 

 amphibia. In hypersecretion of the thyroids, goiter or exophthalmic 

 goiter may result. In the latter, the eyeballs protrude and the pulse 

 is greatly accelerated. Hyposecretion results in colloid goiter, cretin- 

 ism, or myxedema. Cretins are dwarfed, with low mentality, and 

 are frequently deaf mutes. Myxedema (mucous fat) is accompanied 

 by great increase in weight, retarded bone growth, brittle teeth, 

 slow pulse, thickened, wrinkled skin and slow metabolism. Thy- 

 roxin (Kendall) and thyroid extract have been used in the treatment 

 of cretinism, myxedema, and endemic goiter. It is dangerous to 

 start to furnish a community additional iodin in drinking water, 

 as some goitrous persons may be injured. But the campaign of 

 education about the importance of sufficient iodin in food and water 

 (McClendon, Minnesota; and the South Carolina Board of Health) 

 is admirable. 



Applying the discoveries of Bloor, Hill, Sperry and others that 

 under certain intestinal conditions iodin may be discharged from the 

 body in considerable quantities in \\iQ feces, Chidester has suggested 

 that in the cases of water-borne goiter recorded by McCarrison and 

 others, it is quite likely that certain bacteria will cause the liberation 

 of iodin and that subsequent demands made on the thyroid by the 

 excess of unsaturated fatty acids in the intestine will cause thyroid 



1 But Banting and Best in the Journal of Laboratory and Clinical Medicine, 

 1922, Vol. 7, p. 467, gave full credit to E. L. Scott for his pioneer studies, described 

 in 19 1 2 in the American Journal of Physiology, Vol. 29, p. 306. 



