MOSAIC DISEASE OF TOBACCO. 109 



we find in this case that the acti^aty of the agent is not destroyed. Chloro- 

 form in excess, however, does destroy apparently the causal agent of the 

 disease. It is noteworthy that tliis action of chloroform exactly parallels 

 that found to be the case with enzjines. 



ThjTnol, when used in 2 per cent, concentration is very often used as a 

 preventive to bacterial action, and also prevents the growth of fungi. 

 We find, however, that when it is present in concentration not exceeding 

 2 per cent, in the sap the causal agent still possesses its infectious qualities 

 for some time. 



Ether is a substance which, like chloroform, has lipoid-Uke properties, 

 but which has a definite action on the surface tension, lowering it con- 

 siderabl3^ Sap containing ether to the saturation point, which lowers the 

 surface tension from 1 to about .619, was still infectious four months 

 after treatment, although the percentage of infection was much decreased. 



A solution of the sap containing approximately .8 per cent, of actual 

 formaldehyde was very injurious, and at the end of two months no infec- 

 tion was obtained. At the end of ten days in one experiment, however, 

 plants were inoculated and two cases of mosaic disease developed from a 

 series of eight plants, but it is believed that this may possibly have been 

 an accidental infection, as in no other instance was infection obtained. 

 In formaldehyde, however, we have a compound which has a specific 

 narcotic action on certain enzymes aside from its surface activities. 



Where carbolic acid was added to a solution of the sap the active prin- 

 ciple was apparently destroyed. 



In cliloralhydrate we have a substance very soluble in water, but not 

 possessing any relatively great surface activity. It has, however, a specific 

 toxic action on the causal agent of the disease, and even after twenty 

 hours no infection was obtained. These results with chloralhydrate are 

 in complete accord with those obtained in the enzyme work previously 

 mentioned. 



Most of the substances used in the above experiments possess a very 

 definite toxic action to all organisms, particularly bacteria and fungi. 

 As to their effect on the so-caJed ultramicroscopic organisms the writer is 

 unable to state, not having had the opportunity of working with so-called 

 cultures of these organisms. The parallelisms between the surface-ten- 

 sion effects of these substances on enzymes and on the sap containing 

 the active principle of the mosaic disease are very striking. 



Having shown that the causal agent is not bacterial or fungous in 

 character, we must ehminate for the present the supposition of the presence 

 of a toxin or virus in the pathologist's conception of these terms, as it is 

 usual to conceive of these substances as being either the produi^^t of an 

 organism or the activity manifested by the organism itself. As to the 

 production of toxins and viruses by the so-called ultramicroscopic organ- 

 isms httle is known. Noguchi was the first to apparently demonstrate 

 that such organisms do e.xist, and was able to cultivate an organism 

 obtained from the brain of patients suffering from infantile paralysis. 



