THE EXPULSION OF THE UKINE. MICTURITION 1075 



it might be said that this condition is dependent upon an impairment 

 of the resorbing mechanism. 



Let us also remember that the removal of one kidney is not followed 

 by any untoward results, because the opposite organ then enlarges 

 and continues to do the work previously accomplished by the two. 

 The extirpation of both kidneys, however, proves fatal invariably, the 

 animal dying a few days later of uremic poisoning. The same re- 

 sults follow the ligature of both renal arteries. ^ While the conditions 

 of anasarca, ascitis, and others, would furnish many points of physi- 

 ological interest, they more properly belong into the field of general 

 pathology. 



CHAPTER XC 

 THE EXPULSION OF THE URINE. MICTURITION 



The Function of the Ureter. — The duct of each kidney, or ureter, 

 is a muscular tube measuring about 30 to 45 cm. in length. It begins 

 above at the pelvis and terminates below in the wall of the bladder. 

 It is lined by mucous membrane and consists of an inner circular coat 

 of smooth muscle tissue and an outer coat of fibrous tissue. As the 

 small globules of urine escape from the different collecting tubules, 

 they are retained at first in the pelvic cavity until this reservoir has 

 become sufficiently distended. A reflex is then set up which gives 

 rise to peristaltic waves which travel slowly in the direction of the 

 bladder, each contraction forcing a small amount of urine ahead of it. 

 These waves recur at rather regular intervals and increase in frequency 

 as larger amounts of urine are secreted. Their number is usually 3 

 to 6 in a minute and their rate of progression 2 to 3 cm. in a second. ^ 



The activity of the ureter is controlled by nerve fibers derived from 

 the renal plexus as well as from the hypogastric nerves. Their central 

 segments, however, are said to be free from them, although ganghon 

 cells have been detected throughout their entire length. In accordance 

 with this rather deficient nerve-supply, Engelmann^ has formulated 

 the theory that these rhythmic contractions are of myogenic origin. 

 This view finds additional support in the fact that even excised portions 

 of the ureter show a peristaltic activity which may be greatly increased 

 by immersing them in warmed saline solution. Equally convincing 

 data, however, might be submitted in favor of the neurogenic theory, 

 and hence, no definite statements can be made at this time regarding 



1 Pilcher, Jour. Biol. Chem., xiv, 1913, 387. 



2 Heidenhain, Archiv fiir mikr. Anat., 1874; and Protopow, Pfliiger's Archiv, 

 Ixvi, 1897. 



3 Pfliiger's Archiv, ii, 1869. 



