248 On the Musculai* Fibres of the Bladder and Prostate, [June 21, 



and here tlie two sets of very oblique or circular fibres have different axes. 

 Further forward, or towards the apex of the prostate, the space gradually 

 diminishes, the circular fibres of the gland curving in an upward direction 

 into the verumontauum or caput gallinaginis, and blending with the circular 

 fibres of the urethra. While, therefore, the very oblique or circular fibres 

 of the urethra are entirely distinct at one point, they are indissolubly united 

 at another. This is important, as it shows how the sphincter may act in- 

 dependently of the prostate, and the reverse. 



The longitudinal or vertical internal fibres posteriorly, connect the me- 

 dian or central portion of the trigone (trigone vesical, trigonum vesicae, 

 Lieutaud) with the verumontanum in the male, and the uvula and median 

 ridge in the female. The slightly oblique internal fibres bound the trigone 

 laterally, and are continued into the verumontanum, where they cross 

 slightly. The oblique fibres which assist in forming the base of the trigone, 

 are likewise continued in a downward direction on the verumontanum, where 

 they cross, and are mixed up with the continuations of the very oblique 

 fibres which form the sphincter at the neck, and with the circular fibres 

 of the prostate. The arrangement of the fibres in the trigone resembles 

 that found at the cervix and fundus generally, and the author is of opinion 

 that Sir Charles Bell was in error when he described the muscles of the 

 ureters " as separate structures. 



The ureters enter the vesical parietes at a very obtuse angle, and the angle 

 increases according to the degree of distension of the bladder. These tubes 

 receive accessions of fibres from the longitudinal, slightly oblique, oblique, 

 and very oblique external and internal fibres of the bladder in their vicinity, 

 and are continued upon each other within the bladder in the form of a 

 strong transverse band. The transverse band which connects the ureters 

 together within the bladder, or between the uretral orifices, is equal in vo- 

 lume to the ureters themselves within the vesical parietes. The band in 

 question is best seen when the base of the bladder is detached and held 

 against the light, and seems to be formed by the obliteration of the uretral 

 tubes between the uretral orifices. 



The uretral channels seek the internal surface of the bladder even more 

 obliquely than the ureters, and the inner walls of the ureters become so 

 thin, particularly towards the uretral orifices, that they act mechanically 

 as moveable partitions or valves, as in the smaller veins*. The canals 

 of the ureters are consequently closed, partly by the contractions of the 

 muscular walls, and partly by the mechanical pressure exercised by the 

 urine about to be expelled. 



From the foregoing description it will be evident that the various sets of 

 external and internal fibres forming the bladder, urethra, and prostate are 

 antagonistic, not only as regards themselves, but also as regards the territory 

 or region they occupy ; the loops formed by the anterior fibres crossing 



* " On the Eelations, Structure, and Functions of the Yalves of the Vascular System 

 dn Vertebrata," by the author, Trans. Roy. Soc. Edin. p. 763. 



