July 24, 1916 Properties of the Virus of Mosaic Disease 



651 



the talc, which was mixed with water and poured upon the paper. This 

 filter must be very carefully made, as bubbles and cracks which may 

 form as a result of shrinkage due to drying during the process of making 

 render the results unreliable. Filtration was accomplished by means of 

 a reduced pressure of approximately 3 inches of mercury. 



Table II.- 



-Infectivity of mosaic virus after having been filtered through different thick- 

 nesses of powdered talc, U. S. P., in igi 5 



Experiments (Table III) have shown that thick layers of talc, by 

 adsorption, remove all the peroxidase from the pure virus. If no peroxi- 

 dase reactions are shown, or if these reactions have been appreciably 

 weakened, such nitrates have always lost their infectious properties. By 

 reducing the amounts of talc, however, the peroxidase content may be 

 increased until limits are reached beyond which the infective principle 

 also passes into the filtrates. In some of the writer's filtration tests the 

 first portions of the filtrate, giving intense peroxidase reactions, possessed 

 no infectious properties, while the last portions contained the infectious 

 principle of the disease. By using known quantities of powdered talc 

 and constant quantities of different concentrations of virus, it is readily 

 shown that the peroxidase content of the filtrates is not definitely related 

 to infectivity. The Hirsch porcelain funnel was used as in preceding 

 talc filtration tests. The virus was first filtered through paper to remove 

 suspended material. All dilutions were made with distilled water. 

 Filtration was accomplished by means of a reduced pressure of approxi- 

 mately 3 inches of mercury. 



