At the extremity of the cervical canal the instrument comes in contact with a slight obstacle, the internal os, where there exists a narrowing. In the normal uterus, and especially in young girls, the instrument passes this point under slight pressure into the uterine cavity. The amount of pressure which may be used is a question of individual experi ence, generally the weight of the instrument itself is sufficient. It is at this point that the parenchyma of the uterus is most likely to be injured. It should never be forgotten that the sound is intended to glide along an already existing canal, and that it forms with the finger in the vagina a single or double lever with very unequal arms, so that whatever pressure is made at the handle is transmitted much intensified to the point of the instrument. Great resistance at the internal os is only infrequently due to marked and lasting narrowness of the canal. Strictures of the os, which are seldom met with, generally yield to prolonged pressure by the knob of the instrument. In general, marked narrowing of the os is due to swelling of the cervical mucous membrane, or to the not infrequent flexion found at this point, or, finally, to the presence of new growths. In the event of marked narrowing at the internal os we may often determine with the sound the extent in millimetres. The instrument is then pressed upon, even as is a catheter through a callous stricture, the pressure being gradually increased as the sound enters deeper and deeper, and we may feel the uterus move as it is lifted up upon the instrument. In women who have borne many children, in whom the internal os has been widened by collections of fluid, the presence of new-growths or of inflammatory processes in the mucous membrane or the parenchyma, it is frequently impossible to tell when we pass the site of the internal orifice. Only ex. °optionally then do we feel the limit between the transversely roughened mucous membrane of the cervix and the smooth membrane of the uterus.
The passage of the sound by the internal os is generally accompanied by an unpleasant sensation to the patient. Ordinarily the feeling is the same as that which precedes the onset of the menses. In case of narrow canal, however, and in sensitive individuals, there frequently results uterine colic, which may be intense. The appearance of a drop of blood on the withdrawal of the sound is not uncommon, and it points always to injury of the mucous membrane and must be looked upon as abnormal and undesirable.
By means of the previous bimanual examination we are already in formed as to the position of the uterus, and therefore we know the curve which we must give the instrument. In every position of the uterus where the body lies forward, and therefore in case of the normal position, the sound enters with its concavity forwards and upwards and the handle rests against the perineum.
Flexions of high degree necessitate the giving of a sharp curve to the instrument. This is accomplished best by means of the finger in the vagina, which pushes the uterus backwards and upwards. During this manipulation we are able to differentiate between a marked stenosis at the internal os and a narrowing due to flexion.
When the uterus lies backwards the sound is directed downwards from the internal os with its concavity downwards, and in case of flexion the • procedure is the same as for anterior distortion, only that the direction of the instrument is different.
As soon as the instrument reaches the fundus the hand is generally conscious of it, and the sensation to the patient is that of a slight shock. In case of a relaxed uterus, especially the puerperal, but very slight pressure should be made, since the point of the sound may readily pene trate the tissue of the uterus and even through the organ. Attempts at lifting the organ on the sound or at feeling the extremity through the abdominal walls are almost always forbidden in such cases. On the way to the fundus we may test the condition of the uterine mucous membrane by gentle pressure with the extremity of the sound along the anterior and posterior wall. By drawing the sound backwards and foiwards with care it is possible to detect the presence of tumors in the cavity, and in favorable cases the nature of the union of these tumors with the uterus. During these same manipulations we obtain an idea of the movability of the organ.
When the instrument has been passed to the fundus it is steadied by the hand of the examiner or by an assistant, and then by resorting to the simple or the combined vaginal touch we may determine the position of the uterus when steadied by the sound in relation to the other pelvic organs or to tumors. Movements imparted to these tumors while the sound is in the uterus often lead to valuable results.
To measure the depth of the uterine cavity the index finger in the vagina is placed along the sound close to tho external os; the other fingers surround the instrument; which is then withdrawn in the reverse direction from which it was inserted, taking care lest the index finger slip.
Even the experienced examiner may find difficulty in passing the thick metallic sound into the uterine cavity in cases where the passage is dis torted by the presence of tumors. In such cases an elastic catheter may be need after the manner recommended by Sims. Since the catheter armed with its stylet is altogether too inflexible, and yet since without it the heat of the body renders it too soft to pass by the external and in ternal orifices, Sims recommended to pass the catheter with its stylet to the internal os, and then to withdraw the stylet slightly when the catheter becomes flexible at the portion which enters the uterine cavity, and it may feel its way beyond the internal os. This method, however, is not the best, seeing that the instrument bends on itself, and the results of meas urement, therefore, are to be taken only cunt grano.
In the lateral position the sound is passed either under the guidance of one or two fingers or after exposure of the cervix through the specu lum. It is undeniable that it is easier to pass the sound in this way, especially since the cervix may be steadied by a tenaculum and flexion may be in a measure effaced by the exerted traction. By means of such traction with the tenaculum a flexion, in case the uterus is movable, is lessened in the direction of the pelvic axis; and in instances of flexion with fixation of the body of the uterus the cervix should be drawn in the direction opposed to that of the flexion—that is to say, in case of anteflexion backwards, and in case of retroflexion forwards.