THE URINARY ORGANS. 257 



The function of the suprarenal gland is not known. 

 Its extirpation in the dog is followed by death in a 

 few days. There are at least three interesting clini- 

 cal features connected with this organ : 



1. Suprarenal extract, taken internally, increases 

 arterial tension by contracting the small arterioles. 

 The extract has the same effect when sprayed upon 

 surfaces, therefore it is much used in nose, throat, 

 and eye work, to check hemorrhage and reduce con- 

 gestion. 



2. The cortical cells may produce a malignant 

 growth called a hypernephroma. The malignant 

 cells may invade and replace the kidney. The 

 growth usually spreads to the liver and adjacent or- 

 gans, causing death in one to three years. 



3. Addison's Disease is a chronic, usually tubercu- 

 lar, inflammation of the suprarenal glands, fatal in 

 one or two years. It is accompanied with a striking 

 bronze pigmentation of the skin, and digestive and ner- 

 vous disturbances. It is a rare disease of middle life. 



The above facts support the view that the organ 

 secretes a substance that is regularly gathered up by 

 the blood. This secretion may control, in a measure, 

 arterial pressure. The organ is also a relay in the 

 sympathetic nervous system which, when destroyed, 

 as in Addison's Disease, accounts for the gastric and 

 nervous symptoms. 



THE KIDNEYS. 



The kidneys, two in number, are compound tubular 

 epithelial glands derived, embryologically, from the 

 mesoderm. They are situated behind the peri- 

 17 



