1866.] 



of the Bladder and Prostate, 



245 



vertical fibres, the deeper ones being flattened from above downwards, and 

 resembling circular fibres. 



These loops are directed towards the apex and base, and are arranged in 

 four sets ; an anterior and a posterior set which are largely developed, and a 

 right and left lateral set which are accessory and less fully developed. The 

 bladder is consequently bilaterally symmetrical. 



The superficial loops are confined principally to the anterior, posterior or 

 lateral aspects, but the deeper ones radiate and expand towards the apex 

 and base, so that they come to embrace the entire circumference of the 

 bladder in these directions. The expansion of the fibres is greatest towards 

 the apex, and the aggregation of the terminal loops of the anterior and 

 posterior fibres at the cervix (assisted by the lateral fibres) form a well- 

 marked sphincter vesicae in this situation. The fibres pursue definite but 

 varying courses, those which are longitudinal or vertical at one point be- 

 coming slightly oblique at a second, oblique at a third, and very oblique or 

 transverse at a fourth. The fibres consequently change their direction and 

 position on the vesical parietes gradually and according to a fixed principle. 

 The principle involved is readily explained. The most external and most 

 internal fibres are always the most vertical and most feebly developed ; those 

 which succeed or follow becoming more and more oblique and stronger and 

 stronger. The fibres from this circumstance are divisible into two orders, 

 viz., an external and an internal, and these, as has been stated, are grouped 

 in two principal and two subsidiary sets. The two principal sets occur on 

 the anterior and posterior aspects of the viscus, and are so arranged that 

 the terminal or transverse portions of the anterior set intersect the more 

 vertical portions of the posterior set nearly at right angles and the reverse. 

 Similar remarks apply to the subsidiary sets. Between what may be called 

 the vertical or longitudinal and the circular or transverse fibres, other fibres 

 having different degrees of obliquity occur. These consist for the most 

 part of the deeper anterior and posterior spiral fibres, and of the subsidiary 

 spiral fibres from the sides. There is consequently no part of the vesical 

 parietes in which longitudinal, slightly oblique, oblique, and very oblique 

 external and internal fibres may not be found. The additional strength 

 secured by this arrangement cannot well be estimated. 



The external and internal fibres are similarly disposed on the anterior, 

 posterior, and lateral aspects, and if the dissection be conducted from with- 

 out inwards, the fibres first removed are the mesial, vertical, or longitudinal 

 fibres ; then the slightly oblique fibres inclined on either side, and crossing 

 at acute angles as in an attenuated figure of 8 ; then the oblique fibres, 

 crossing at wider vertical angles as in the more perfect figure of 8. Lastly, 

 the very oblique fibres, crossing at such obtuse angles as to have been, up 

 to the present, regarded as circular fibres. The fibres which are still deeper 

 and which constitute the proper internal fibres, have a precisely similar 

 arrangement, but are rudimentary, and consequently not so readily traced. 

 The external and internal fibres, as will be seen from this description, be- 



