SECRETION. 413 



tacles are nucleated, transparent cells often containing oil-globules and 

 a yellowish-brown pigment. Beneath the capsule is the zona glomer- 

 ulosa, with cells in round groups; the next is zona fasciculata, with 

 cells in columns ; and the last is zona reticularis. 



The medullary substance is composed of very irregularly shaped 

 cells, rather closely, 'but irregularly, packed into a meshwork of fibrous 

 tissue. In the interstices lie masses of multinucleated protoplasm, 

 blood-vessels, and an abundance of nerve-fibers and cells. The cortex 

 of the adrenals arises from the mesoderm ; the medulla of the adrenals 

 is a direct outgrowth of the sympathetic nervous system from the 

 neural ectoderm. 



The cells of the medulla are conspicuous in that they contain 



Fig. 151. Effect of Adrenalin on the Volume of Inspired and Expired 

 Air. Tracing with Gad's Aeroplethysmograph. 



First line, normal. Second and third lines, showing the diminution of 

 volume of air inspired. 



certain reducing agents. The agent which gives color-reactions has 

 been termed cliromogen. Just what this agent is chemically is not 

 known, but it is believed to be the principle which raises blood-pres- 

 sure when suprarenal extracts are injected subcutaneously. The 

 active principle is, according to Abel, epinephrin; according to 

 Takamine, adrenalin. Adrenalin has been prepared synthetically by 

 Professor Hans Meyer, of Marburg, from methylaminoorthodioxy- 

 acetphenon. It constricts arterioles, contracts the iris, and produces 

 glycosuria, like adrenalin. The cortex of the adrenals secretes 

 choline. 



Adrenalin is a white, crystalline substance with bitter taste, 

 slightly soluble in water, and stable in dry state. It absorbs oxygen 

 from the air, and is a strong reducing agent in alkaline and neutral 

 solution. Its solution becomes red on standing. Chemically, it 



