454 METABOLISM, NUTRITION, AND DIET 



The daily output of energy for the adult man is as follows: 



Kilogrammeters. Calories. 



1,898,034 or 4,467 



This estimate is relatively high for ordinary activity as determined by 

 Atwater and others. It is indeed more energy than the standard diets in 

 the table given on page 450 will yield to the body. For example, Voit's 

 diet yields 3,055 calories, and the average of the table is only 3 . 125 calories. 



THE INFLUENCE OF THE DUCTLESS GLANDS ON METABOLISM. 



A further question to be considered is the relationship between the metab- 

 olism of the tissues and the products of the metabolism of other tissues. 

 The metabolism of one tissue may produce products, protein or otherwise, 

 which when taken up by the blood and carried to other tissues supply ex- 

 actly what is necessary for their complete anabolism. 



The physiology of the internal secretions has revealed a number of such 

 influences that are best explained on the assumption of the presence of spe- 

 cial products. 



The Thyroid and Accessary Thyroids. These glands are situated in 

 the neck. The thyroid consists of two lobes, one on each side of the tra- 

 chea, extending upward to the thyroid cartilage, covering its inferior cornu 

 and part of its body; the lobes are connected across the middle line by a 

 middle bar or isthmus. The thyroid is covered by the muscles of the neck. 

 It is highly vascular, and varies in size in different individuals. The gland 

 is encased in a thin transparent layer of dense areolar tissue, free from fat, 

 containing elastic fibers. The gland vesicles are each lined with a single 

 layer of cubical cells and are filled with transparent nucleo-albuminous 

 colloid material. 



The accessory thyroids possess the structure of the thyroid and apparently 

 perform the same function. 



The colloid material which is formed within the thyroid and accessory 

 thyroid vesicles, and is believed to be their secretion, finally ruptures through 

 their walls into the lymph channels and thus gains entrance to the circulation. 

 The secretion of the thyroid falls into the class known as internal secretions, 

 and exerts an influence upon the metabolic processes of the body, probably 

 through its influence on the central nervous system. Complete extirpation 

 of the thyroid, at least in some animals, produces death, preceded by a group 

 of characteristic symptoms. In man and the monkey the symptoms after re- 

 moval come on slowly and resemble the disease known in man as myxedema. 



