GENERAL OBSERVATIONS. 137 



muscular and internal coats. It has been conjectured, that their 

 termination in exhalents on the surface of the bladder are re- 

 markably numerous. 



The veins correspond with the arteries ; but they are very 

 numerous on the lower and lateral parts of the bladder, and by 

 uniting with the veins of the rectum form a remarkable 

 plexus. 



The Lymphatic Vessels of this organ do not appear more 

 numerous than those of other parts. They pass on each side 

 of the bladder in the course of its blood-vessels, and unite with 

 the larger lymphatics, and the glands which lie upon the great 

 blood-vessels on the sides of the pelvis. 



The Nerves of the bladder are derived both from the inter- 

 costal nerve and from the nerves of the medulla spinalis which 

 pass off through the sacrum ; and therefore the bladder is more 

 affected than the viscera of the abdomen, by injuries of the 

 medulla spinalis. 



The action of the muscular fibres of the bladder in expelling urine, and the 

 effect of those fibres which are situated near the orifice of the urethra in 

 retaining it, can be considered with more advantage after the structure of the 

 urethra and the muscles connected with that canal have been described. 



It has been stated that the internal coat of the bladder is very sensible ; but it 

 may be added, that in consequence of disease about the neck of the bladder, 

 the natural sensibility appears most inordinately increased. When the inten- 

 sity of pain which accompanies these complaints, the frequent recurrence of 

 paroxysms, and their duration, are taken into view, there seems reason to 

 believe that none of the painful affections of the human race exceed those 

 which arise from certain diseases of the bladder. Happily these diseases are 

 not very common. 



The functions of the kidneys is to secrete urine, and that of the bladder to retain 

 it, until the proper time for evacuation. 



The urine may be regarded as an excrementitious fluid, which contains many 

 substances in solution that are constantly found in it, and many others that 

 are occasionally in it, which are taken as aliment or medicine, and pass to 

 the bladder with little, if any change. The odor of the roseleaf, the color of 

 rhubarb, &c., are occasionally perceived in urine. 



The substances constantly found in urine are numerous. The chemical account 

 of the subject is so long that it cannot be detailed here ; but the student ought 

 to make himself acquainted with it, and he will read with great advantage 

 some of the modern treatises on Physiology and Animal Chemistry, and also 

 Thomson's Elements of Chemistry. 



12* 



