On either side of the point K may be seen the orifices, M M, of the ureters, opening upon two ridges of fibrous substance directed towards the uvula. These are the fibres which have been named by Sir Charles Bell as "the muscles of the ureters;" but as they do not appear in the bladder when in a state of health, I do not believe that nature ever intended them to perform the function assigned to them by this anatomist. And the same may be said of the fibres, which surrounding the vesical orifice, are supposed to act as the "sphincter vesicae." The form of that portion of the base of the bladder which is named "trigone vesical" constitutes an equilateral triangle, and may be described by two lines drawn from the vesical orifice to both openings of the ureters, and another line reaching transversely between the latter. Behind the trigone a depression called "bas fond" is formed in the base of the bladder. Fig. 2, Plate 56, represents the prostate of a boy nine years of age. Fig. 3, Plate 56, represents that of a man aged forty years. A difference as to form and size, &c., is observable between both. [Illustration: Abdomen, showing blood vessels and other internal organs.] Plate 56--Figure 1, 2, 3 COMMENTARY ON PLATES 57 & 58. CONGENITAL AND PATHOLOGICAL DEFORMITIES OF THE PREPUCE AND URETHRA.--STRICTURE AND MECHANICAL OBSTRUCTIONS OF THE URETHRA. When any of the central organs of the body presents in a form differing from that which we term natural, or structurally perfect and efficient, if the deformity be one which results as a malformation, ascribable to an error in the law of development, it is always characterized as an excess or defect of the substance of the organ at, and in reference to, the median line. And when any of the canals which naturally open upon the external surface at the median line happens to deviate from its proper position, such deviation, if it be the result of an error in the law of development, always occurs, by an actual necessity, at the median line. On the contrary, though deformities which are the results of diseased action in a central organ may and do, in some instances, simulate those which occur by an error in the process of development, the former cannot bear a like interpretation with the latter, for those are the effects of ever-varying circumstances, whereas these are the effects of certain deviations in a natural process--a law, whose course is serial, gradational, and in the sequent order of a continuous chain of cause and effect. Fig. 1, Plate 57, represents the prepuce in a state of congenital phymosis. The part hypertrophied and pendent projects nearly an inch in front of the meatus, and forms a canal, continued forwards from this orifice. As the prepuce in such a state becomes devoid of its proper function, and hence must be regarded, not only as a mere superfluity, but as a cause of impediment to the generative function of the whole organ, it should be removed by an operation.