226 



PATHOGENIC BACTERIA. 



inside out In this manner a mould of the test-tube is 

 formed. The test-tube is next constricted to a degree that 

 will not interfere with the future introduction of culture- 

 media in a fine pipette or inoculation with a platinum 

 loop, and that will permit of ready sealing in a flame 

 when necessary ; the rounded end is then cut off, and 

 the edges are smoothed in a flame. The collodion bag is 

 now carefully fitted over the end of the tube, shrunken 

 on by a gentle heating, and cemented 

 fast with a little fresh collodion ap- 

 plied to the line of union. Novy rec- 

 ommends that a thread of silk be 

 wound around the point of union, to 

 hold the collodion in place and to aid 

 in handling the finished sac. It now 

 appears as in Fig. 43, b. 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 

 hangs suspended in the water it con- 

 tains. The whole is now carefully sterilized by steam. 

 When ready for use, a tube of bouillon is inoculated 

 with the culture intended to be placed in the animal ; 

 the water in the capsule is then pipetted out, and is re- 

 placed by the inoculated bouillon carefully introduced 

 with a pipette. The constricted portion is then sealed 

 in a flame, and the capsule picked up with forceps and 

 introduced into the peritoneum by an aseptic operation. 



Fig. 43. — Prepara- 

 tion of collodion sacs : 

 a, test-tube constricted 

 and cut ; b, sac attached 

 to the tube. 



