THE INFLUENCE OF THE DUCTLESS GLANDS ON METABOLISM 427 



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 423 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 one tissue and the products of the metabolism of other tissues. 

 The metabolism of one tissue may produce products, proteid 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. The thyroid gland is situated in the neck. It con- 

 sists of two lobes, one on each side of the trachea, extending upward to the 



FIG. 311. Part of a Section of the Human Thyroid, a, Fibrous capsule; b, thyroid vesicles 

 filled with, e, colloid substances; c, supporting fibrous tissue; d, short columnar cells lining vesicles; 

 /, arteries; g, veins filled with blood; h, lymphatic vessel filled with colloid substance. (S. K. 

 Alcock.) 



thyroid cartilage, covering its inferior cornu and part of its body; these lobes 

 are connected across the middle line by a middle lobe or isthmus. The 



