Catgut.—It is far more difficult to prepare catgut, but, since it is necessary for ligation, the following methods may be considered best:
The commercial catgut as made from the intestines of sheep, is wound snugly upon a rod of glass and thoroughly brushed with soft soap and hot water. It is then rinsed free of soap, wound upon small glass spools, and placed for forty-eight hours in a one-per-cent alcoholic bichlorid solution, composed of bichlorid of mercury, 10 parts; alcohol, 800 parts; distilled water, 200 parts. The turbid fluid produced by first immersion is changed. Before using, the spools are placed in a glass vessel contain containing a 1-2,000 sublimate alcohol (Schaffer), made up as follows:
| Bichlorid of mercury | gr. vj; |
| Alcohol | ℥x; |
| Distilled water | ℥iiss. |
These glass cases are obtainable for the purpose and contain a second perforated compartment for the ligatures passing through rubber valves placed into the openings (Haagedorn).
Catgut is generally prepared by soaking in oil of juniper for one week and then retaining it in absolute alcohol (Kocher), or a 1-1,000 alcoholic sublimate solution.
Another method for strengthening catgut, as well as to prevent its too rapid absorption, is to chromatize it. This is done as follows:
The catgut is placed in sulphuric ether for forty-eight hours, then treated for another forty-eight hours in a ten-per-cent solution of carbolized glycerin, followed by a five-hour subjection to a five-per-cent aqueous solution of chromic acid (Lister). It is allowed to remain in the latter forty-eight hours, then placed in an antiseptic, dry, tightly closed receptacle, and finally soaked in 1-20 carbolic solution before using.
The formaldehyd method of Kossman is to immerse the gut in formaldehyd for twenty-four hours, then washing with a solution of chlorid and carbonate of sodium and retaining it in the same solution. The catgut in this procedure swells and its strength is much impaired in this way.
Any of the above methods are not above criticism, however, rigid as they may seem, bacterial growths having been obtained with nearly all of them.
The dry-air method (Boeckman, Reverdin) is reliable, but the subjection of catgut to dry air at a temperature of 303° F. for two hours results in making it tender and less pliable.