CIRCULATION OF BLOOD AND OF LYMPH 171 



amount of this secretion is probably just enough to cause the 

 walls of the arteries to maintain a certain amount of contrac- 

 tion, thus preventing them from being too lax. 



Other Ductless Glands. There are several other ductless 

 glands, one connected with the thyroid called the parathyroid ; 

 one connected with the brain, pituitary body. The pancreas 

 also, besides furnishing digestive juices to the intestines through 

 its duct, gives other important substances to the body through 

 the blood. The exact and entire function of these ductless 

 glands is not fully understood. 



One must not presume, however, that these glandular organs 

 just mentioned are the only ones which pass into the blood 

 as it goes through them substances which are essentially 

 hormones in character. Probably it is safe to say that every 

 tissue in the body makes its contribution and in this way sends 

 material to every other tissue, definitely influencing it in one 

 way or another. 



In health, then, each tissue gives out its own hormone in such 

 quantity and of such quality that all other tissues are benefited 

 by it. This fact should come to us as a suggestion that, by 

 careful eating, breathing, sleeping, and exercise, each tissue is 

 kept strong and healthy and so contributes to the strength and 

 health of the whole body. 



