2l6 MANUAL OF BACTERIOLOGY. 



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. Formalde- 

 hyde 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 bot- 

 tle. 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 respec- 

 tively. If left too long in the solution, 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 for- 

 maldehyde solution. Up to this time the gut has not been 

 sterihzed. It has undergone a chemical change whereby it 

 may be boiled without spoihng it. The sterihzation 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-ringed fruit-jars, sterilized by boiling. 

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

 cent, of glycerin. To sterihze the glycerin it should be placed 

 in a bottle in water and raised to the temperature of boiling 

 water for half an hour. 



To make chromicized catgut wind the spools as before. 

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

 1.5 grams; glycerin and carbohc acid, each, 10 c.c; water, 

 I Hter. 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 

 a heavy retaining suture, and is prepared by washing the 

 strands in ether to free from fat. Soak in a 4 per cent, solu- 



