128 



Scientific Proceedings (38). 



80 (490) 



Filtration through collodion sacs. 

 By EDNA STEINHARDT. 



[From the Hygienic Laboratory, University of Michigan^ 



Toxins, ferments, and protein solutions have been filtered 

 through collodion membranes by many investigators but the 

 results have varied to a considerable degree. The following ex- 

 periments may explain this variation. 



Collodion sacs were made and mounted on glass tubes, accord- 

 ing to the Novy technique. Before filtration, the empty sacs were 

 immersed in water and submitted to air pressure (three inches of 

 mercury) ; if perfect, they were then used. The filtration was 

 done under a 2-inch vacuum. After the filtration the sacs were 

 again retested by air pressure. If still perfect, the filtrate was then 

 used for experimentation. 



In this manner diphtheria toxin was filtered. One hundredth 

 of a cubic centimeter of this toxin killed a guinea-pig in 39 hours. 

 Three cubic centimeters of the undiluted toxin were filtered through 

 a collodion sac, and one hundredth of a cubic centimeter of this 

 filtrate killed in 38 hours, none of the toxin having been held 

 back by the filter. However, if the toxin was diluted, 1 to 100 

 before filtration, one cubic centimeter of the filtrate failed to kill, 

 causing only slight induration. 



When dilute cobra venom was filtered, all toxicity was lost. 

 On filtering successive quantities of this venom through the same 

 collodion sac, the filtrate gradually became toxic, until the fourth 

 filtrate was practically of the same strength as the control. 



This result is in accord with the work of Marbe {Compt. rend. 

 Soc. de biol., 1909, lxvii, 809) on the filtration of agglutinins 

 through collodion sacs, and also with the passage of complement 

 through a Berkefeld filter, as shown by me {Jour. Med. Research, 

 1904, xiii, 409), and later found by Muir and Browning {/our. of 

 Path, and Bact., 1909, xiii, 232) working on the same subject. 

 Evidently filtration through collodion sacs, as through the Berke- 

 feld filter, is a phenomenon of adsorption, the substances in solu- 

 tion passing through when adsorption has reached a certain degree. 



By altering the concentration, the quantity to be filtered, and 



