Collodion capsules 



229 



an exact mold of the tube is formed. If a small opening be made 

 at the end of the tube over which the sac is molded, and the tube 

 filled with water after being properly coated with collodion, a small 

 amount of pressure, applied by blowing gently into the tube, will 

 force the water between the collodion and glass and so detach it 

 without inversion. A test-tube of the same size is next constricted 

 to a degree that will not interfere with the future introduction of 

 culture-media in a fine pipet or inoculation with a platinum loop, 

 and that will permit of ready sealing in a flame when necessary; 

 the rounded end is cut off, and the edges are smoothed in a flame. 

 The upper open end of the collodion bag is 

 carefully fitted over the end of the tube, shrunk 

 on by a gentle heating, and cemented fast 

 with a little fresh collodion applied to the line 

 of^union. Novy recommends that a thread 

 of silk be wound around the point of union, to 

 hold the collodion in place and to aid in han- 

 dling the finished sac. The sac is next filled 

 with distilled water up to the thread, the tube 

 is plugged with cotton, and the whole placed 

 in a larger test-tube containing distilled water, 

 the cotton plug being packed tightly around 

 the smaller tube, so that the collodion sac does 



not reach the bottom of the large tube, but „. tj 



, , ,. , . . rr,, Fig- 79- — Prepara- 



hangs suspended in the water it contains. The tion of collodion sacs: 



whole is now carefully sterilized by steam. «. Test-tube constric- 



When ready for use, a tube of bouillon is in- '^t^f.^'l^^i t^it'" ''" 

 oculated with the culture intended to be placed 

 in the animal, the water in the capsule is pipetted out and replaced 

 by the inoculated bouillon carefully introduced with a pipet, the con- 

 stricted portion is sealed in a flame, and the capsule picked up with 

 forceps is introduced into the peritoneal cavity by an aseptic 

 operation. 



The collodion capsules may be made of any size. Those for rabbit 

 experiments should be of about 10 cc. capacity, those for guinea-pig 

 experiments about 5 cc. By coating large glass tubes they can be 

 made of 500 cc. capacity, the large bags being useful for chemic 

 dialysis. 



