PREPARATION OF INSTRUMENTS, ETC. 



the process of soaking in formaldehyde and the consequent 

 shrinking, one strand crosses another, the one next to 

 the glass will be so pressed upon as to prevent hardening 

 at that point. When the gut is boiled later in water, 

 that point will gelatinize and break at the least strain. 

 Formaldehyde comes in a 40 per cent, solution. We use a 

 3 per cent, solution, pouring one part of the 40 per cent, 

 formaldehyde solution and thirteen parts of water into a 

 wide-mouthed bottle. Immerse the spools in this solution 

 for periods of time varying with the size of the gut. No. o 

 is left in one hour. Nos. i, 2 and 3 are given three, five, 

 and seven hours respectively. If left too long in the solu- 

 tion the gut will become too hard, too brittle, and the 

 strength will be impaired. Wash in running water for a 

 longer time than it was in the formaldehyde solution. Up 

 to this time the gut has not been sterilized. It has under- 

 gone a chemical change whereby it may be boiled without 

 spoiling it. The sterilization of the gut consists in boiling 

 for fifteen minutes, with the receptacles in which it is to be 

 kept. With sterile forceps place the spools, each size by 

 itself, in wide-mouthed-ground-glass-stoppered bottles or in 

 rubber-sealing fruit jars, sterilized by boiling. Pour over 

 the gut clean 95 per cent, alcohol with 8 to 10 per cent, of 

 glycerine. To sterilize the glycerine it should be placed in 

 a bottle in water and raised to the temperature of boiling 

 water for half an hour. 



To make chromicizcd catgut wind the spools as before. 

 Place the spools in a solution of : bichromate of potassium, 

 1.5 grammes; glycerine and carbolic acid each 10 c.c. ; water 

 I liter. Allow them to remain in this solution for twenty- 

 four hours. Take out and drain, allowing them to dry for a 

 few hours. Then place in the formaldehyde solution and 

 put through the same process as with formaldehyde catgut. 



Kangaroo tendon, owing to its slow absorption, is used as 



