UROGENITAL SYSTEM, 353 
the interrenal tissue is on the outer side of the adrenal organ, the su- 
prarenal forming the inner portion. In the amphibia the adrenals are 
closely connected with the mesonephroi, being attached to their 
inner margins (urodeles) or to the ventral surface (anura). In the 
reptiles they are lobulated structures near the gonads. In the mammals 
they are more compact (often called suprarenals) and are placed at the 
anterior end of the kidneys, often unsymmetrically. 
Both organs are regarded as glands of internal secretion, their 
product being passed directly into the blood. The secretion of the 
medullary portion (suprarenal) of the mammals is adrenalin, an acti- 
vator or hormone, which by its action on the muscular system causes 
an increase in the blood pressure. Even less is known of the function 
of the interrenal. Certain observations render it probable that the 
secretion of this is of value in destroying certain products of metabolism 
which otherwise might be injurious to the organism. 
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