VISCERAL ANATOMY. 141 



THYMUS GLAND. 



This is a gland lying at the back part of the neck, under the 

 trachea, and partly within the thorax. It has two lateral lobes in 

 contact with each other, and is only found in the foetus and young 

 animal. 



Structure. 



Of lobules, which contain spaces filled with granular matter. 



The lymphatics are well marked. 



URINARY ORGANS. 



They comprise the kidneys, ureters, bladder and urethra (in the 

 male this is also genital). 



THE KIDNEYS. 



The essential organs of the urinary system are two in number, 

 situated in the abdomen, to the right and left of the sub-lumbar 

 region, against the psoas muscles. The peritoneum passes under 

 them. The right is heart-shaped and more anterior than the left, 

 which is bean-shaped. 



Weight. Right, twenty-seven ounces; left, twenty-five. 



Each kidney has a superior and inferior flattened surface, an 

 external convex border and an internal concave one, which is 

 deeply notched, and called the hilum. The hilum lodges the 

 vessels, nerves and beginning of the ureter. 



Interior. 



A section shows that at the hilum is found a cavity, called the 

 pelvis, the beginning of the ureter, elongated from before back- 

 ward. Opposite this, in the proper tissue of the kidney, is seen 

 a ridge, on which empty the uriniferous tubes. The pelvis is 

 lined with mucous membrane. 



Structure. 



Fibrous coat or capsule,, most external, and sending prolonga- 

 tions into its interior. 



Parenchyma. Divided into an external or cortical and internal 

 or medullary layer. The cortical layer is darker, and contains 

 small, round bodies, the Malpighian corpuscles. The medullary 

 is lighter, and contains the uriniferous tubules. There is also 

 some connective tissue supporting the tubes, vessels, etc. 



