INCISIONS. 135 



4tli. Incisio7is by Slices — Scraping or Shaving Incisions. — 

 These incisions are made by dividing the tissues in successive lay- 

 ers. Three varieties of operation are practiced, differing accord- 

 ing to the density of the tissues acted upon. In the first, which is 

 apphcable to hard structures, the bistoury, or, preferably, the sage 

 knife is required. The instrument is held full in the hand, as a 

 table knife, or, again, as the bow of a violin, and is passed flatwise 

 over the sm-face of the tissues, and layers of various thicknesses 

 removed from it ; and sometimes the tissues are sufficiently hard 

 to requii-e the strength of both hands for the management of the 

 instrument. 



Fig. 163.— Sharp Tenaculum. 



In a second mode, applicable to soft tissues, a convex bistouiy 

 and a paii' of forceps or a sharp tenaculum are necessary. Rais- 

 ing with either of these a thin layer of the tissue to be divided, 

 the bistoury is carried sUghtly flatwise over the siu'face and a piece 

 of it is cut, scraped, or shaved ofl", the operation being repeated 

 until the desired depth has been reached. 



A third mode is applied in cases of growths which are to be 

 cut off at their base. To do this, the growth is raised as much as 

 possible, by means of the forceps or tenaculum, and the amputation 

 is accompHshed with a few sawing movements of the instrument. 



The forms which incisions may receive are of two principal 

 kinds — the simple and the cornpound. 



Simple incisions are those which are generally made with one 

 stroke of the bistoury, and generally from without inward, 

 and are either straight or curved. The straight, or simple, are 

 indicated for the exposure of regions, the oj)ening of abscesses, 

 etc., etc' They are not as applicable to the removal of tumors, 

 especially of those which have large bases. The curved incisions 

 vary in their circular shape, and diiier also from the straight in 

 the modus operandi, as they require a stretching of the skin to 

 be made in various directions, as that of the bistouiy is changed 

 over the cutaneous surface. 



Compound incisions are formed by the union of several simj)le 

 incisions, their number varying much, but they may be reduced 



