CHAPTER in 

 THE ADRENAL GLANDS, THE GONADS, AND THYMUS 



Like the pituitary, each adrenal gland is a double gland, that 

 is, consists of two distinct portions, united together, one might 

 say, by the accident of birth. It would be confusing, however, 

 to speak of each as two glands, because there are, as a matter 

 of fact, two separate adrenal glands, one in the right side of the 

 abdomen, and the other in the left. Each gland is composite, or 

 duplex. How the two parts came to be united is a long story, 

 interesting but too long to be recounted here. In fishes they are 

 apart and independent. 



Each adrenal is a cocked hat shaped affair, astride the kidneys, 

 easily recognized because of its yellowish fatty color. Indeed, 

 for centuries the glands were not given a separate status as 

 organs, but were passed up as part of the fat ensheathing the 

 kidney. In childhood and youth, in common with the other 

 glands, they are relatively larger and more prominent than in 

 the adult. Also, at every age, the amount of blood passing 

 through them is very large compared to their size. Their tre- 

 mendous importance in the body economy accounts for their 

 being so favored. 



The two parts of which each gland is composed, are known as 

 the cortex or outer portion (literally the bark) and the medulla 

 or inner portion (literally the core). No clean-cut boundary 

 sharply delimits the two, as strands and peninsulas of tissue 

 of one portion penetrate the other. In the history of their devel- 

 opment in the species and the individual, and in their chemistry 

 and function, a sharp difference contrasts them. 



In the embryo, the cortex is derived from the same patch that 

 gives rise to the sex organs, the ovaries in the female, and the 

 testes in the male, described as the germinal epithelium. How 

 intimately the two sets of glands are connected is neatly pointed 

 by this fact of a common ancestor. All vertebrates possess 



