132 INTERNAL OR MUCOUS COAT OF THE BLADDER. 



Harrison,* who has investigated it most recently, thus 

 describes it : " When the several strata of longitudinal fibres 

 have been raised from the front and lateral parts of this region, 

 the circular fibres of the bladder become distinct, but do not 

 appear so proportionably increased as were the longitudinal ; 

 but on detaching more completely the longitudinal strata, down 

 to the circumference of the very opening of the urethra*, a dis- 

 tinctly fibrous, that is, muscular tissue is evident, bounding this 

 opening laterally and superiorly, but not below. This muscu- 

 lar fasciculus is not intimately connected to the general circular 

 coat ; it appears redder and of a closer texture, and will be 

 found to be attached to the fibrous or tendinous substance, 

 forming the anterior part of the trigone on each side of the 

 uvula, behind which it does not pass. The longitudinal fibres 

 are inserted partly into this semicircular muscle, much in the 

 same manner as the levatores ani are inserted into the circum- 

 ference of the anus. This structure we consider to be partly 

 elastic but essentially muscular ; it bounds the urethral opening 

 laterally and above, but not below ; the slight projection of the 

 uvula in the latter situation, and the elasticity and gentle state 

 of contraction natural to all the sphincter muscles, will preserve 

 this opening in a constantly closed state during the quiescent 

 and normal condition of the parts/' 



For a description of the muscles of this part somewhat analo- 

 gous to the above, see Dr. Horner's Anatomy, vol. ii. p. 80, 

 4th edit. 



The cellular substance between the muscular and internal 

 coats is dense. It yields in a remarkable manner to distension, 

 and recovers its original dimensions very easily. From its 

 analogy to a similar coat in the intestines, it is called the Ner- 

 vous Coat. 



The Internal Coat of the bladder is of a light color in the 

 dead subject, when it has been free from disease. It has been 

 called villous improperly ; for the villous structure is not appa- 

 rent upon its surface. Being continued from the integuments 

 of the body which are extended along the urethra, it has been 

 inferred, that the surface of this coat was formed by the epi- 



* Vide article Bladder, by J. Harrison, Cyclop, of Anat. and Physiology. p. 



