July 24.1916 Properties of the Virus of Mosaic Disease 671 



SUMMARY 



In this paper are given the results of a study of the properties of 

 the virus of the mosaic disease of tobacco, and evidence is adduced to 

 show that the infective principle can not be identified with peroxidase. 

 Briefly, the facts obtained may be stated as follows: 



(1) The infective principle of the mosaic disease of tobacco is retained 

 by the Livingstone atmometer porous cup used as a filter, and also by 

 powdered talc. Although the filtrates may show intense peroxidase reac- 

 tions, they no longer produce infection. 



(2) The infective principle of the disease is quickly destroyed in alcohol 

 of a strength of 75 to 80 per cent. In this strength precipitation of the 

 peroxidase is complete. ■ By filtering the solution the peroxidase may be 

 collected, freed from alcohol by evaporation, and redissolved with water. 

 This solution gives intense peroxidase reactions, but no longer produces 

 infection. Alcoholic solutions of virus of 45 and 50 per cent strengths 

 did not destroy the infective principle of the disease within the same 

 period. In these solutions the pathogenic agents are not destroyed and 

 appear to be carried down with the precipitate, leaving the supernatant 

 solution without infectious properties, although giving strong peroxidase 

 reactions. 



(3) By the addition of different quantities of hydrogen peroxid to 

 the virus, it is possible to find a concentration of sufficient strength to 

 destroy the peroxidase, but leaving little or no free peroxid in the solution. 

 Such solutions no longer show peroxidase reactions, but retain their 

 infectious properties for a long time. A considerable excess of hydrogen 

 peroxid destroys the infective principle itself. The quantity of hydrogen 

 peroxid required to destroy the peroxidase without leaving any consider- 

 able excess in the solution depends upon the nature of the virus, the 

 amount of active catalase present, etc. 



(4) The virus was treated with formaldehyde for 31 days in the follow- 

 ing concentrations: One part formaldehyde in 100, 200, 400, 600, 800, 

 1,000, 1,200, and 1,500 parts of virus solution. The solutions containing 

 1 part formaldehyde in 800, 1,000, 1,200, and 1,500 parts of solution gave 

 infection. Stronger concentrations were no longer infectious, although 

 giving intense reactions for peroxidase. 



(5) Ether, chloroform, carbon tetrachlorid, toluene, and acetone failed 

 to extract either the infective principle or the peroxidase from dried 

 mosaic material. These solvents also failed to destroy the infectious 

 principle in this material. Ethyl and methyl alcohol completely destroyed 

 the infective principle in the leaf material itself, as well as in the extract. 

 No evidence of peroxidase was obtained in the alcohol extracts. Glycerin 

 does not destroy the infective principle of the disease. Water extracts 

 of dried material not only show peroxidase reactions, but also contain the 

 infective principle of the disease. 



(6) A precipitate of aluminum hydroxid, formed by adding aluminum 

 sulphate to alkaline solutions of virus, appeared to carry down the infec- 



