^34 



Experimentation upon Animals 



must be twirled alternately within and without the collodion, so 

 that it is equally distributed upon its surface. When the desired 

 thickness is attained, and the collodion is sufficiently firm, the tube 

 is plunged under water and the hardening process checked. 



A cut is next made around the upper edge of the coUodion film, 

 and it is removed by carefully turning it inside out. In this manner 

 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 intro- 

 duction of culture-media in a fine pipet or 

 inoculation with a platinum loop, and that will 

 permit of ready seahng 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 httle fresh 

 coUodion appHed 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 handling 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 hangs suspended in the water it contains. The 

 whole is now carefully sterihzed by steam. 



When ready for use, a tube of bouUlon is inoculated 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 constricted 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 lo 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. 



Fig. 75. — Prepara- 

 tion of collodion sacs : 

 a, Test-tube constric- 

 ted and cut; b, sac at- 

 tached to the tube. 



