BXCRETIOK. 4GU 



rious lengths, among which, again, the deepest cells of the epithelium 

 are found spheroidal, irregularly oval, spindle-shaped or conical. 



The Urinary Bladder. The urinary bladder, which forms a re- 

 ceptacle 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 situate above and behind, being termed the fundus; and the narrow 

 constricted portion in front and below, by which it becomes continuous 

 with the urethra, being called its cervix or neck. 



Structure. It is constructed of four principal coats serous, mus- 

 cular, areolar or submucous, and mucous, (a.) The serous coat, which 

 covers only the posterior and upper part of the bladder, has the same 

 structure as that of the peritoneum, with which it is continuous. (I) 

 The fibres of the muscular coat, which are unstriped, are arranged in 

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

 longitudinal, 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 vesicce. The muscular fibres of the bladder, like 

 those of the stomach, are arranged not in simple circles, but in figure- 

 of-8 loops, (c) The areolar or submucous coat is constructed of connec- 

 tive tissue with a large proportion of elastic fibres, (d) The mucous 

 membrane, which is rugose in the contracted state of the organ, does 

 not differ in essential structure from mucous membranes in general. 

 Its epithelium is stratified and closely resembles that of the pelvis of the 

 kidney and the ureter (fig. 297). 



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 both medullated and non-medullated fibres, 

 both branches from the sacral plexus (spinal) and hypogastric plexus 

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

 of the nerve-fibres. 



The Urine. 



Physical Properties. Healthy urine is a perfectly transparent, am- 

 ber-colored liquid, with a peculiar, but not disagreeable odor, a bitterish 

 taste, and slight acid reaction. Its specific gravity varies from 1015 to 

 1025. On standing for a short time, a little mucus appears in it as a 

 flocculent cloud, consisting chemically, it is said, of nucleo-albumin and 

 not mucin. 



Chemical Composition. The urine consists of water, holding in solu- 

 tion 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. 



