Otis also devised an instrument known as the _urethrometer_, which is of value in the accurate estimation but not necessary in the treatment of many cases. [Illustration: FIG. 29 Urethrometer.] These instruments may be passed down to the bulbous portion of the urethra; beyond this further investigation should be made with the ordinary sounds. By their use much may be determined in regard to prostatic tenderness, and the combined use of the sound in the deep urethra with the finger in the rectum will give more accurate information regarding the size of the prostate than can easily be obtained in any other way. Much reaction, however, may occur from the use of the sounds in this way, and it is a good rule never to introduce an instrument into the deep urethra without having ample reason therefor, and then doing it under antiseptic precautions; while, as a formal measure after it, the patient should be placed at absolute rest. This serious reaction, which occasionally follows instrumentation of the deep urethral passage, is commonly known as _urethral fever_. It is characterized by chills, elevation of temperature, and often by local indications, the constitutional features being sometimes pronounced, and in rare cases terminating fatally. Such serious symptoms are difficult to explain. Doubtless the use of the instrument opens up paths of fresh infection, and absorption rapidly follows, which may be limited to the surrounding tissues or cause widespread trouble. This may ensue after every precaution has been adopted, although doubtless many of these cases have been the result of carelessness and failure in antisepsis. Much may be done in the way of prevention when this condition is feared, for these cases are rarely so urgent but that the urine can be medicated and its quality improved, while a part of the procedure may consist in having the patient empty the bladder and then carefully washing it, or filling it with an antiseptic solution, which may be expelled before any instrument is used except the catheter, through which it may be necessary to introduce the bladder wash. The administration of 2 or 3 Gm. doses of urotropin, with or without quinine, previous to the exploration, may also be of great service. The surgeon perhaps does not always take these precautions, but he should when the history of the case shows that patients have already suffered in this way. In the presence of such a history the urethra should be explored with great caution.