'Wherefore taking a catheter proportionate to the age and sex we prepare the instrument for use. The mode of preparation is this: having bound a little wool round with a thread and introduced the thread by means of a sharp rush into the pipe of the catheter, and having cut off the projecting parts of the wool with a pair of scissors, we put the catheter into oil. Having then placed the patient on a convenient seat and used fomentation, if there be no contra-indication we take the catheter and introduce it direct down to the base of the penis, then we must draw the penis up to the umbilicus (for at this part there is a bend in the passage), and in this position push the instrument onwards. When in the perinaeum it approaches the anus we must bend the penis with the instrument in it down to its natural position, for from the perinaeum to the bladder the passage is upwards, and we must push the instrument onwards till we reach the cavity of the bladder. We afterwards take out the thread fastened into the opening of the catheter, in order that the urine, being attracted by the wool, may follow as happens in syphons.' It is occasionally, in cases of cancer of the prostate, of service to adopt this proceeding to prevent the eye of the catheter from getting blocked before the bladder is entered, but it is strange that Galen should have fallen into the mistake of thinking that it is necessary to set up a syphon action, as he was well aware of the expulsive power possessed by the bladder; in fact, his explanation of the physiology of urination is almost up to date. Celsus gives a good description of the catheter both male and female (VII. xxvi): Res vero interdum cogit emoliri manu urinam, quum illa non redditur, aut quia senectute iter eius collapsum est, aut quia calculus vel concretum aliquid ex sanguine intus se opposuit: ac mediocris quoque inflammatio saepe eam reddi naturaliter prohibet. Idque non in viris tantummodo, sed in feminis quoque interdum necessarium est. Ergo aeneae fistulae fiunt; quae ut omni corpori ampliori minorique sufficiant, ad mares tres, ad feminas duae medico habendae sunt; ex virilibus maxima decem et quinque digitorum, media duodecim, minima novem, ex muliebribus maior novem, minor sex. Incurvas vero esse eas paulum, sed magis viriles, oportet, laevesque admodum; ac neque nimis plenas neque nimis tenues.