ON THE CATGUT LIGATURE 113 



dilute solution of chromic acid. But minute as is the quantity of the chromic 

 acid, it exerts, when in conjunction with carbolic acid, a most powerful influence 

 upon the gut. The first effect of the addition of the carbolic acid to the chromic 

 solution is to change its pale yellow colour to a rich golden tint. But if the 

 liquid is allowed to stand without the introduction of the catgut, it changes 

 in the course of a few hours to a dingy reddish-brown in consequence of some 

 mutual reaction of the two acids, and a certain amount of grey precipitate is 

 formed. If, however, catgut about equal in weight to the carbolic acid is added 

 as soon as the ingredients are mixed, the liquid retains its brightness, and the 

 only change observed is a gradual diminution of the depth of the yellow colour ; 

 the precipitate, if it still occurs, taking place into the substance of the catgut. 

 As soon, therefore, as the preparing liquid has been made, catgut equal in weight 

 to the phenol is^introduced into it. If you have too large a proportion of catgut, 

 it will not be sufficiently prepared ; if you have too small a quantity, it may 

 run the risk of being over-prepared.^ At the end of forty-eight hours the chromic 

 element of the liquid has nearly spent itself, and the process of preparation is 

 complete. The catgut is then taken out of the solution and dried, and, when 

 dry, placed in i to 5 carbolic oil ; it is then fit for use. I have here a sample of 

 catgut prepared by this method. Although it has been steeped in warm blood- 

 serum since this morning at eleven o'clock, it is still translucent and firm without 

 being rigid, and a reef-knot tied upon it holds with the most perfect security. 



The strength of the catgut depends upon different circumstances. In the 

 first place, sheep differ as to the strength of their intestines ; and the catgut- 

 maker, if he understands his business, will insist upon having his raw material 

 of a proper kind. In the next place, the intestines must not be allowed to 

 putrefy — they must be used when quite fresh. For these things you must, 

 of course, rely upon the maker of the catgut. In the next place, the preparing 

 liquid causes a certain amount of softening of the catgut, and if it is introduced 

 in loose hanks, this will tend to produce a little uncoiling of the twisted cord, 

 and a still greater degree of uncoihng will take place during drying. It is of 

 very great importance that this should not occur, because it involves weakening 

 of the thread, and that in different degrees in different parts ; and this may 

 lead to the gut giving way when you subject it to a strain. The catgut, then, 

 should be prepared on the stretch both when it is put to soak and when it is 

 put to dry. 



I need not enter into the mode in which this can be done by the manu- 

 facturer. I may only say this, that the surgeon who wishes to prepare it himself 



^ A moderate excess of the licjuid, not exceeding twice the prescribed amount, does not produce 

 any serious degree of over-prep^iratitju. 



