174 ANATOMY OF THE DOMESTIC FOWL 



cuboidal cells as are also the collecting tubules. The collecting 

 tubules originate from every part of the internal substance of the 

 lobules, and extending to the gyrations, uniting in the pinniform 

 structure and traversing to the margin of the lobules, following along 

 the uneven surface, infero-laterally and toward the median body line, 

 finally empty into the ureter. 



There are many arterial branches given off from the arteria re- 

 nalis. The arteries which supply the kidneys are given off from the 

 posterior aorta and ischiadic artery. As soon as these arteries enter 

 the kidney they break up into two systems. One system supplies 

 the kidney substance with nourishment in the form of nutrient blood; 

 the second system supplies the glomerules with what may be con- 

 sidered functional blood (Gadow). The second system of arteries 

 branches into the small arteria interlobularis, which pass between 

 the lobules of the kidneys where they give off side branches which 

 penetrate the cortical portion of the lobules and form the capillary 

 plexus, the glomerule. 



The arteriole that enters into the structure of the glomerule is 

 lined with endothelial cells and is surrounded by a few muscle fibers 

 and a fine network of connective tissue. The vessel that carries the 

 blood away is similarly constructed. 



Function. In the glomerules the liquid portion of the urine is 

 filtered out of the blood, which urine flows through the uriniferous 

 tubules and passes from the kidney through the ureter. In the 

 cubical cells are extracted the solid portions of the urine which also 

 pass through the tubules with the liquid. The urinary secretion, 

 as found in the ureter, does not contain much liquid, but, on the con- 

 trary, is made up of a pasty material consisting of salts which are, 

 for the most part, uric acid crystals and sodium urate (Fig. 52, B). 

 This material becomes hard, like cement, soon after being exposed 

 to the atmosphere. This secretion may be noted as a whitish pasty 

 material on the outer parts of the feces, or droppings, voided by the 

 birds. 



The Ureter. Location. The ureter extends along the inferior sur- 

 face of the kidney. It has its origin near the anterior extremity of 

 the kidney, and passing posteriorly the entire length of the kidney 

 receives tributary collecting tubules, and terminates in the upper 

 wall of the cloaca in the urodeumal portion. 



Shape. The ureter gradually enlarges in diameter until it reaches 



