PREPARATION OF INSTRUMENTS, ETC. 21 7 



tion of chromic acid for twenty-four hours. Then steriHze by 

 the cumol method. 



Silk may be sterilized by the fractional method (see p. 51) 

 as this does not impair the strength as does boiling. 



Silkworm gut is prepared by steam steriUzation by the frac- 

 tional method or by boihng in plain water for one-half hour. 

 It should not be boiled in soda solution, as this spoils the gut. 



Horsehair strands are cut into two-foot lengths, washed 

 with soap and water and sterilized with steam by the frac- 

 tional method. They make a very fine suture and are used 

 where an inconspicuous scar is particularly desirable, as on 

 the face. Only the finer grades are used for this purpose. 



Silver wire* This material has the advantage over other 

 suture materials of having a germicidal or at least a restrain- 

 ing influence on bacteria. If we remember that absolute 

 sterilization of the skin is not possible by any means, we must 

 see that in silver wire as a skin suture we have a safe and 

 valuable material. Recent annealing by heating to a dull red 

 increases the flexibility of the wire but almost totally destroys 

 its germicidal property. This will reappear in a month and 

 is not disturbed by boihng. Therefore prepare it by boiling 

 for ten minutes in the i per cent, soda solution. 



Sponges. The best absorbents to use in surgical work are 

 those whose sterility is undoubted. Pads of gauze are easily 

 steriUzed by steam as for dressings. Sea sponges f may be 

 prepared by beating with a wooden mallet to remove sand 

 and dirt. Soak in a 1-64 solution of hydrochloric acid for 

 twelve hours to remove lime deposits. Wash in running 

 water. Soak for fifteen minutes in a saturated solution of 

 permanganate of potassium, then place in a saturated solu- 

 tion of oxalic acid until they are perfectly bleached. After 



* Bolton. Transactions Association American Physicians. 1894. 



t McBurney. International Text-book of Surgery. June, 1900. P. 284. 



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