562 FILTERABILITY OF MICRO-ORGANISMS 



Tetanus toxin is unaffected by filtration through any gypsum filter, but, as has 

 long been known, is removed in limited quantities by siliceous filters. If freshly 

 gelled, pure colloidal silica is drawn into a Berkefeld filter, one obtains a siliceous filter 

 through which tetanus toxin may be passed to giye a filtrate of which one may inject 

 up to an equivalent of fifty minimal lethal doses for the guinea pig without killing the 

 animal. With the ordinary Berkefeld filter I have never succeeded in producing a 

 filtrate of which one might inject more than the equivalent of ten minimal lethal 

 doses without killing the pig. 



Watery infusions of the various neurotoxic drugs and toxins not of bacterial origin 

 were drawn through both classes of filters with the intention of removing, if possible, 

 the neurotoxic components. A solution of cobra venom containing 2 mg. per cubic 

 centimeter was found to be fatal to mice in doses of 0.5 cc. by paralysis of respiration 

 within one hour. The filtrate obtained by passage of the solution through the gypsum- 

 magnesia filter was equally toxic. The filtrate from the Berkefeld colloidal silica filter 

 was non-toxic. 



Solutions of the venom of Crotalus airox, the western diamond rattlesnake, in 

 normal saline solution 2 mg. to the cubic centimeter in doses of i cc, were found to 

 be fatal to mice within ninety minutes, with paralysis of respiration and a marked 

 hemorrhagic reaction at the site of infection. The gypsum-magnesia filtrate was 

 equally toxic; the filtrate from the Berkefeld colloidal silica filter was not toxic. Solu- 

 tions of the venom of Crotalus terrificus, the Brazilian rattlesnake, were found to pass 

 through both filters and retained their toxicities in both instances. 



Diphtheria antitoxin was found to be removed by filtration through the gypsum 

 magnesia filter as well as through the filter made of a Berkefeld reinforced by colloidal 

 silica. Tetanus antitoxin was not removed by either filter. A 2 per cent solution of 

 standardized adrenal powder was rendered inactive by filtration through the gypsum- 

 magnesia filter and passed through the silica filter unchanged. Curare in solution con- 

 taining I mg. to the cubic centimeter, which readily paralyzes a frog, is totally detox- 

 ified when passed through the gypsum filter. Test doses of digitalis, which in the frog 

 arrest the heart in one hour, are rendered non-toxic when filtered through the gypsum 

 filter. 



If one extracts 2 gm. of powdered opium with 60 cc. of water for twenty-four 

 hours and decants the fluid, i cc. of the infusion will paralyze and kill a mouse within 

 fifteen minutes. When filtered through the gypsum-magnesia filter, the extract is no 

 longer toxic. When filtered through the Berkefeld colloidal silica filter, the fluid is 

 toxic. When morphia is added to the gypsum filtrate, i mg. to the cubic centimeter, 

 and again passed through the gypsum filter, the filtrate is again toxic ; and when this 

 toxic filtrate is passed through the Berkefeld colloidal silica filter, the filtrate is non- 

 toxic. If morphia be added to the original opium infusion in amounts equal to i mg. 

 to the cubic centimeter, and the solution be passed through the gypsum filter, the 

 filtrate is still toxic. If it be passed through the Berkefeld colloidal silica filter, it is 

 also toxic. But if it be passed successively through both filters, the final filtrate is non- 

 toxic. 



Morphia is a base and should be and is removed by the silicic acid, but the nar- 

 cotic in the powdered opium is not present as a base, but as an acid, and is removed by 



