MOVEMENTS OF THE BLADDER. 339 



splanchnic nerve of the same side. They are said to cease permanently 

 shortly after ligature of the upper end of the ureter, in consequence of 

 the severance of the nerve fibres. They may occur, however, in the 

 isolated ureter. That this tube is well supplied with sensory fibres is 

 evidenced by the severe pain of renal colic, which occurs on the im- 

 paction of a calculus in the ureter. 



The reflux of urine from the bladder into the ureters is prevented 

 by the oblique manner in which these enter the bladder, a sort of 

 valvular opening being thus formed. 



Movements of the Bladder. 



The urine, which is constantly trickling down the ureters, accumulates 

 in the bladder, whence it is expelled at intervals by the contraction of 

 the muscular wall of this viscus. The act of micturition is in the young 

 child purely reflex and dependent on the tension in the bladder. With 

 advancing age, however, the individual acquires more or less voluntary 

 control over the reflex act. It will be convenient to first consider the 

 purely reflex act of micturition. 



Muscular tissue of bladder and urethra. — The muscular Avail of the 

 bladder is generally described as being composed of three layers — an outer 

 longitudinal, a middle circular, and an inner longitudinal or oblique coat. The 

 division between these coats is, however, by no means well marked, and, as 

 Griffiths has shown, 1 bundles which are longitudinal may become circular or 

 oblique, and bundles of different coats may be continuous with one another. 

 The longitudinal fibres are best marked in the middle of the anterior and 

 posterior surfaces of the bladder. These coats are practically continuous in the 

 female with a similar series of coats forming the muscular wall of the urethra. 

 In the male, according to Griffiths, the bundles are gradually lost in the 

 connective tissue of the neck of the bladder, and are not inserted into any 

 special part, such as the capsule of the prostate of the gland. On the lateral 

 surfaces of the bladder, the oblique and transverse fibres are most apparent. 

 The bundles of muscular tissue on the two sides of the bladder are continuous. 

 The longitudinal fibres of the bladder, with or without the transverse fibres, 

 are often described as the detrusor tirince. 



The apparent necessity for some muscle which by its contraction would 

 close the vesico-urethral orifice, has led many anatomists to ascribe an internal 

 sphincter muscle, formed by a thickening of the circular coats of the bladder 

 at its junction with the urethra. An account of this internal sphincter was 

 given by Charles Bell, 2 and has been repeated in other works on anatomy. 

 Careful dissection, however, fails to show, any thickening of muscle around the 

 commencement of the urethra, sufficient to constitute a sphincter. The absence 

 of such a sphincter has been especially emphasised by Griffiths, and can he 

 easily verified by dissection. There are, however, round the urethra, collec- 

 tions of unstriated and striated muscle, which by their contraction close this 

 canal, and check the urinary flow. Thus the first part of the urethra is 

 surrounded by a muscular coat, consisting of inner longitudinal fibres and an 

 outer thicker circular layer, continuous with the inner and middle layer of the 

 bladder. There is also a sheet of striped muscle, which surrounds the greater 

 part of the urethra, and in the male extends from the level of the entrance of 

 the vasa deferentia into the urethra, to within a couple of inches of the urinary 

 meatus. In man, the first part of this muscle is represented by a few trans- 



1 Journ. Anat. and Physiol., London, 1894, vol. xxv. p. 510. 



2 "Anatomy of the Human Body," 6th edition, 182B, vol. iii. p. 390. 



