434 DR. J. ANDERSON ON THE CLOACAL BLADDERS 



On the Cloacal Bladders and on tlie Peritoneal Canals in Chelonia. 

 By John Anderson, M.D., F.L.S., &c. 



[Bead February 17, 1876.] 



The cloaca in the Chelonia, as is generally known, is an elongated 

 saccular dilatation intervening between the termination of the 

 rectunTand the orifice at the base of the tail, or external anus, and 

 into which certain important structui'es open. It is of consider- 

 able length and transverse capacity, and has exceedingly thin walls, 

 and is directly continuous with the rectum. But on the floor, 

 concealed by closely apposed folds is an anteriorly and downwardly- 

 directed dilatation or chamber, terminating in the orifice of the 

 bladder, and having, opening on its lateral walls, the orifices of the 

 seminal tubes or of the oviducts, according to the sex, and also the 

 openings of the ureters. The folds which close in this chamber 

 for the general cavity of the cloaca are backwardly continued to 

 the base of the glans, enclosing the urino-genital groove. By 

 this arrangement of the folds, the faecal matter in its transit out- 

 wards is prevented from having access to the orifices of those im- 

 portant structures the generative organs and the kidneys, and 

 to the urino-genital groove. In certain Chelonia another fold 

 exists above and slightly posterior to the termination of the rec- 

 tum, having above it on either side tlie large patulous openmgs of 

 the cloacal bladders. This fold springs from either lateral wall of 

 the cloaca ; and those two segments of it meet in the mesial line 

 and constitute an arched forwardly directed fold. In some spe- 

 cies the centre of the arch is taclted to the roof of the cloaca by 

 a narrow longitudinal fold or septum which divides the area which 

 overlies the fold into two halves, into each of which opens a 

 cloacal bladder; while in others the septum does not exist, and of 

 course the area overlying the fold is continuous. 



At the extremity of the urino-genital groove on the floor of 

 the cloaca is the large glans of the penis, and in the opposite sex 

 the identically formed but less developed clitoris. Springing 

 from the sides and base of the glands is a crescentic fold of the 

 mucous membrane, which passes backwards tending towards the 

 mesial line to meet its fellow of the opposite side, thus constitu- 

 ting a hood or rudimentary prseputium for the isolation of the 

 glans penis or clitoridis from the faecal matter of the common cavity 

 of the cloaca, and thus simulating the structure of the Monotremes 



