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Scientific Proceedings (119). 



tube, open at both ends, and sealed in place with a collar of rubber 

 tubing. Sac and V tube are partly filled with water, plugged 

 with cotton and sterilized in the autoclave. Shrinkage during 

 sterilization may be avoided by maintaining a pressure of 10-12 

 cm. of water in the sac. The sac may even be expanded by this 

 method, but its permeability apparently is not thereby increased. 



After sterilization the chosen medium is placed within the 

 sac, and dialysis of nutritive and growth-promoting substances 

 occurs into the surrounding fluid, which is accessible for inoculation 

 through the other limb of the V tube. For anaerobic cultivation 

 both medium and dialysate may be layered with vaseline. The 

 vaseline seal excludes oxygen, but also retains C0 2 and may 

 therefore tend to a more rapid acidification of the medium. 



Osmotic pressure adjustments take place automatically by 

 changes in the levels of medium and dialysate. With experience 

 the approximate osmotic pressure of a given medium may be 

 anticipated and the passage of water into the sac may be avoided 

 by filling it with medium to a higher level. 



These sacs were prepared especially for use with the Smith- 

 Noguchi fresh tissue medium. This medium, consisting of ascitic 

 fluid or dilute serum and a fragment of fresh rabbit kidney or 

 testicle is placed within the sac, in the dialysate of which we have 

 grown subplants of T. pallidum, S. microdentium and Bacterium 

 pneumosintes. Thus the organisms have been obtained free from 

 the confusing, antigenic, protein precipitate which develops in the 

 tissue medium. The addition of dextrose broth hastens the 

 establishment of anaerobic conditions. 



For mass cultures the sacs have been formed in gelatin-lined 

 Erlenmeyer flasks, and enclosed in larger flasks with a glass tube, 

 or spout, fused into the side near the bottom. 



A full description of the sacs will appear in a forthcoming 

 number of the Journal of Experimental Medicine. 



