134 ELEMENTARY OPERATIONS. 



a broad commumcation between the original opening and the one 

 just formed. By using the sharp end of an S probe, passing it 

 alongside the director previously engaged, and pushing it through 

 the side, the maMng of the iacision from without inward may be 

 avoided, as described above, and the groove of the S probe may be 

 used as that of an ordinary director. 



Sometimes, however, when the original opening allows it, the 

 finger is introduced Lato it and used as a conductor. In this case, 

 a blunt bistoury is preferable, as less dangerous to the operator 

 than the straight instrument, or the curved form may be used. 

 This may be made to slide with the back of its blade, or again 

 flatwise, along the palmar face of the finger until the bottom of 

 the wound has been reached, and then turning the knife, the tis- 

 sues are divided by carrying the bistoury either toward or from 



Fig. 163.— Using the Finger as a Director. 



the operator. This procedure is more appUcable when the fistu- 

 lous head is not deep, but it is preferable to the use of the ordin- 

 ary director as being a much better instrument of diagnosis, and 

 safer as a director of the bistoury. 



3d. Subcutaneous Incisions. — The usefulness of this mode of 

 dividing tissues is best demonstrated by its application to cases 

 of tenotomy and myotomy, or the puncture preceding the injec- 

 tion of tincture of iodine according to some methods. It requires 

 special instruments, made with narrow blades or with fine trocars, 

 which, when introduced through the skin, leave a very small open- 

 ing, the division being made under the Hgaments, with special care 

 to avoid its division beyond the point where the instrument has 

 been Lutroduced. Suppuration seldom follows this operation if it 

 has been properly performed, and, accordingly, the cicatrization is 

 very rapid; the great advantage obtained by this mode of incision 

 cannot be overlooked. 



