MOSAIC DISEASE OF TOBACCO. Ill 



Reaction to Antiseptics. — It is stated that the ultramicroscopic organ- 

 isms are not, to any extent, affected by the ordinary antiseptics, and the 

 same is true for toxins in general. On the other hand, enzymes and their 

 activities are very strongly affected by the substances usually made use 

 of as antiseptics, and this is found to be true, with one or two possible 

 exceptions, in the case of mosaic sap. It has been shown that formalin, 

 carbolic acid, chloralhydrate, and even chloroform in excess, will inhibit 

 the activities of the causal agent in mosaic sap, while, on the other hand, 

 such substances as ether, toluol, thymol and chloroform in dilution have 

 little or no effect. While all three classes are to a certain extent affected 

 by antiseptics in general, the enzyme group is most strongly affected, and 

 in the case of the mosaic we find this reaction; also, as has been pointed 

 out, the effect of substances possessing marked surface-active properties 

 is, in the case of mosaic sap, quite analogous to that of these substances 

 on enzymes. It had been hoped to carry on more detailed work on this 

 point, but as yet no opportunity has offered to take up this phase of the 

 matter. AUard^ has studied the effects of alcohol, ether and other sub- 

 stances on mosaic sap, and an interpretation of his results, with particu- 

 lar reference to the surface-active properties of the substances under con- 

 sideration by him, parallel the author's findings in the case of enzymes to 

 a marked degree. It is believed that more work of this character might 

 throw considerable light on this matter. 



Activity. — So far as can be judged from laboratory results the activity 

 of the causal agent in mosaic sap is continuous, and as this holds true not 

 only for organisms but, within limits, for enzymes and toxins as well 

 this property cannot be made use of for differential purposes. 



"Koch's Laws" or "Postulates," so called, are followed by all three of 

 the classes under consideration, and the same is true in the case of mosaic 

 disease; the causal agent obeys these laws, and might well be placed in 

 any one of the classes so far as this property is concerned. 



The Kitasato filter has been used by some as a means of separation of 

 "ultramicroscopic" organisms from enzymes and toxins, and although 

 the arbitrary use of any one filter as a standard, unless the size of pores, 

 adsorption properties, thickness of walls, etc., are carefully taken into 

 consideration, may be open to question, this procedure has been followed 

 in some instances in animal pathology, and it has been found that the 

 Kitasato filter held back the organisms and that no infection could be 

 obtained from the filtrate. In the case of the mosaic disease, however, we 

 find that apparently, as has been previously indicated in this paper, 

 where large volumes are used, the causal agent passes through the Kitasato 

 filter, and we do get infection from the filtrate. 



The disease is infectious, but whether the infection may be indefinitely 

 transferred through several plants with undiminished virulence is open 

 to question. On some varieties of tobacco this does not apparently take 



1 Allard, H. A.: Some properties of the virus of the mosaic disease of tobacco. Journal Agr. 

 Research, Vol. VI., No. 17 (July, 1916). 



