404 EXCRETION 



thirteenth dorsal nerves. They reach the kidney by way of the splanchnic 

 nerves and the renal plexus to the renal artery along which they run into 

 the substance of the kidney. Berkely has demonstrated nerve plexuses 

 about the arterioles and around Bowman's capsule. Terminal knob-like 

 endings of nerve fibrils were shown. Some authors have claimed renal vaso- 

 constriction following vagus stimulation, but the fact seems not to be uni- 

 versally admitted. 



The Ureters and Urinary Bladder. The duct of each kidney, the 

 ureter, is a tube about the size of a goose-quill and from twelve to sixteen 

 inches in length. It is continuous above with the pelvis of the kidney, and 

 ends below by obliquely perforating the walls of the bladder and opening 

 on its internal surface. It has three principal coats, an outer fibrous, a 

 middle muscular, of which the fibers are unstriped and arranged in three 

 layers. The fibers of the central layer are circular, and those of the other 

 two layers longitudinal in direction. It has an internal mucous lining con- 

 tinuous with that of the pelvis of the kidney above and the lining of the 

 urinary bladder below. The urinary bladder, which forms a receptacle for 

 the temporary lodgment of the urine in the intervals of its expulsion from 

 the body, is more or less pyriform. Its widest part, which is situated 

 above and behind, is termed thefundus; and the narrow constricted portion 

 in front and below, by which it becomes continuous with the urethra, is 

 called its cervix or neck. It is constructed of four principal coats: serous, 

 muscular, areolar or submucous, and mucous. The fibers of the muscular 

 coat deserve special mention. They are unstriped, are arranged in three 

 principal layers, of which the external and internal have a general longitu- 

 dinal, and the middle layer a circular, direction. The latter are especially 

 developed around the cervix of the organ, and are described as forming a 

 sphincter vesicae. The mucous membrane is provided with mucous glands, 

 which are more numerous near the neck of the bladder. 



The bladder is well provided with blood and lymph vessels and with 

 nerves. The latter are from the sacral plexus (spinal) and hypogastric 

 plexus (sympathetic). Ganglion cells are found, here and there, in the 

 course of the nerve fibers. 



THE URINE. 



Quantity and General Properties. Healthy urine is a perfectly 

 transparent amber-colored liquid, with a peculiar but not disagreeable odor, 

 a bitterish salty taste, and a specific gravity of from i .020 to i .025. The 

 urine consists of water holding in solution certain organic and saline matters 

 as its ordinary constituents, and occasionally various other matters. Some 

 of the latter are indications of diseased states of the system and others are 

 derived from unusual articles of food or drugs taken into the stomach. 



