The internal or cystic opening of the urethra is a slit, the mucous membrane lining which is thrown into longitudinal folds; the external orifice is an oval vertical opening f inch long. There are often two pro jections of the muco.us membrane from the anterior orifice, which, meet ing behind in the urethral wall, join the hymen externally, and give a rosette appearance to the orifice of the urethra. The diameter of the urethra, some I inch, can be greatly increased by means of instruments.
The following are the most important differences between the female and the male bladder: in the woman the organ is broader and rounder, and is less deep antero-posteriorly, since the genitals are pla,ced between. it and the rectum. As a rule the capacity of the female bladder is greater than that of the male; 6+ pints have been found in it in cases of reten tion. In the male the fundus of the bladder rests securely against the an terior rectal wall; but in the female this is not the case. IIere the anterior and posterior vaginal walls are so subject to dislocations and lesions, that the bladder is often displaced, and its fundus loses all support when there is considerable pressure from above and the labial cleft is open. There is also some difference between the sexes in regard to the extent to which the peritoneum covers the posterior bladder wall. It does so to a much less extent than in the male, being reflected at the level of the internal os from the bladder to the uterus. The relations of the female bladder to its surroundings are very important; as we see if we examine Fig. 1 p. and Fig. 3 p. 11. The round and broad ligaments, the uterus and the ovaries, the small intestine and the vermiform process, are all in relation to one another. So often does disease in these neighboring organs affect the bladder, that there are a large number of maladies of that organ which occur in women, and do not occur in men. We need only call to mind the various changes in shape and position caused by uterine displace ments, or the perforations of the bladder caused by extra-uterine ketal sacs, or stones caused by perforating fu3tal bones or by hairs from dermoid cysts of the ovary. And so also we may mention inversion of the vesical mucous membrane as an example of a disease that only occurs in the fe male bladder.
As regards the mucous membrane of the bladder, we notice that be sides the few round or oval crypts, and the simple or branched acinous glands, there are found at the fundus in some cases solitary lymphatic fol licles and closely-packed rounded papilhe. According to Landau the epithelium of the urinary bladder is extremely elastic, so that it can suffer very considerable extension without solution of continuity. Oberdieck, experimenting with rabbits, found that it consisted of four layers; first one of large, flat, irregular cells with round or oval nuclei; then one of cubical cells with long processes at their lower borders; then a layer with thin processes that dip down into the connective tissue; and lastly a layer of small round or oval cells with large nuclei and karyokinetic figures. These latter are the replacement cells of the epithelia.' layer of
the vesical mucous membrane. Stretching the bladder obliterates the folds of the mucous membrane, and diminishes the thickness of the epi thelium, chiefly through a change of position of the cylindrical cells of the third layer. In five ca.ses Oberdieck could demonstrate only once the presence of crypts lined with cylindrical epithelium in the rabbit's bladder. As is well known, the bladder possesses a triple muscular layer, whose thickly interlaced fibres form the detrusor urinal muscle, and at the ostium urethrale form a perfect sphincter. About one inch behind or above the orificium vesicale urethrae two small tumors are formed by the ureters as they bore their way through the vesicular wall; they are united together by the so-called lig-amentium inter-uretericum (compare p. 17 Fig. 7). It was formerly supposed that the closure of the ureters was effected only by the fold of mucous membrane which the oblique position of the ureter in the vesical wall caused; but JuriCs later inves tigations show that it is brought about by the elastic tension of the muscu lar fibres among which the vesical extremity of the ureter lies.
In many vesicular diseases it is of importance to decide how the inner surface of the bladder acts as an absorbing organ. L. Schafer Diss. Giessen, 1870) believes that under normal conditions of urination, there is a constant though small absorption of water by the walls of the bladder; and he believes that he has proved this by finding that after the produc tion of a vesical fistula in animals, the urinary secretion was increased 2.3 to 4.5 per cent. On the other hand Susini ' injected solutions of iodide of potassium and infusion of belladonna into his own bladder, but was unable either to detect the former in the sputum, or to appreciate any physiological action from the latter, even after several hours reten tion. The results obtained by Allen 2 agree with this, as do the experi mental conclusions of P. Dubelt concerning the origin of vesical catarrh. It seems hardly to be doubted that while the urethral mucous membrane readily absorbs when in its normal state, the vesical mucous membrane with uninjured epithelium does not absorb substances like strychnine, morphine, atropine, and iodide of potassium, save when its epithelitun has been injured or is diseased. Cazenave and Lipine, on the other hand, found that not only the normal constituents of the urine, but uric and phosphoric acids, were absorbed; and Landau could, after the injection of of one per cent. solution of iodide of potassium and chloride of lithium in two cases, demonstrate iodine once in the sputum, and prove the absoiption of lithium once by spectral-analysis.