:}96 THE MAINTENANCE OF THE INDIVIDUAL 



grotesque results. Fortunately this condition may l)e alleviated in 

 the early stages by the addition of iodine to the diet, or in advanced 

 cases, by extirpation of a portion of the gland. 



Occasionally an individual gives evidence of an underactivity of 

 the thyroid gland. In such a case, the amount of thyroxin produced 

 by the gland is actually decreased. Well-defined and characteristic 

 symptoms result. Ingested food is not utilized, with the result that 

 the excess is soon deposited as fat, and definite obesity becomes visible. 

 Certain other symptoms are quite characteristic, as a slowing down of 

 the mental and nervous activities, which may result finally in feeble- 

 mindedness or imbecility. If the thyroid gland be hereditarily de- 

 fective or non-functional a lamentable condition known as cretinism 

 develops. In such cases skeletal development is arrested and a stunted 

 misshapen individual results since normal growth becomes impossible. 

 This condition is alleviated by administering thyroxin. 



Parathyroids 



The parathyroid glands, likewise outgrowths of the pharyngeal 

 region of the body of nearly all vertebrates, vary slightly in number 

 and position with the form under consideration. In man, there are 

 normally four parathyroid glands having a total weight of not over 

 0.4 gram. Nevertheless, they persist during life and are now known to 

 play a very important part in maintaining the calcium balance of the 

 body, and by means of it, the irritabiUty of the cells. The active 

 hormone of the parathyroid glands was demonstrated by Hanson in 

 1925 and later isolated by Collip. 



While the exact nature and method of the functioning of these 

 glands is not thoroughly understood, it is known that their removal 

 is usually fatal. The first effect of the removal of these glands is that 

 the calcium salts are reduced and the threshold of stimulation thereby 

 lowered ; the peripheral nerves and muscles of the organism become 

 more irritable and the various reflexes become extreme. Severe 

 muscular contraction, or tetanus, finally results and the death of the 

 organism usually ensues unless calcium is added to the blood. This 

 may be done by the injection of the hormone or solutions of calcium 

 salts. 



Pancreas 



While the pancreas has long been recognized as a gland secreting 

 various important digestive enzymes, it was not until 1889 that it 



