APPARATUS USED IX THE EXPERIMENTS. 17 



gas as a disinfectant. The object of his investigation was to deter- 

 mine the effect of the gas on pathogenic bacteria. An exhaustive 

 study was made of the subject and included delicate tests of the 

 efficacy of the several means of generating the gas. The results of 

 McClintic's work indicate the superiority of the formalin-perman- 

 ganate method of generating the gas; therefore this method was used 

 in the present experiments. In this method, formalin, a solution of 

 formaldehyde in water, is poured on crystals of potassium perman- 

 ganate ; a vigorous reaction takes place, with sufficient heat to liberate 

 a large quantity of formaldehyde gas. water vapor, carbon dioxid, 

 and a small quantity of formic acid. The potassium permanganate 

 is decomposed by a part of the formalin, and the heat of this reaction 

 serves to liberate formaldehyde gas from the remaining formalin. 



The first American pathologist to employ the gas in the control 

 of fungous diseases was Jones. a of Vermont. His experiments were 

 confined to the treatment for potato scab, and pastils were used 

 to generate the gas. In subsequent work conducted by Jones and 

 Morse, & the formalin-permanganate method was employed for gen- 

 erating the gas. Still later reports on the same line of work, the 

 prevention of potato ^cab. were made by Morse c> at the Maine Agri- 

 cultural Experiment Station. 



All of these experiments demonstrated the efficacy of formaldehyde 

 gas as a disinfectant, but as potatoes and not cultures of the fungus 

 were dealt with, the exact effect on the latter is still an unsolved 

 problem. 



J. E. Higgins/* of the Hawaii Agricultural Experiment Station, 

 conducted preliminary experiments with formaldehyde gas as a 

 means of checking pineapple rot. These were made in connection 

 with investigations to determine the most efficient means of handling 

 and shipping the Hawaiian fruit. Although the experiments were 

 on a small scale they indicated the advantage of this means as a pro- 

 phylactic measure. 



APPARATUS USED IN THE EXPERIMENTS WITH THE FUNGUS. 



In the experiments with the fungus Thielaviopsis paradoxa, con- 

 ducted by this office, it was necessary to provide an especially con- 



a Jones, L. R. Potato Diseases and Their Remedies. Thirteenth Annual Re- 

 port. Vermont Agricultural Experiment Station, 1S99-1900, pp. 26S-2S1. 



b Jones, L. R., and Morse, W. J. Potato Diseases and Their Remedies. 

 Eighteenth Annual Report, Vermont Agricultural Experiment Station, 1904-5, 

 pp. 272-291. 



c Morse. W. J. Prevention of Potato Scab. Bulletins 141 and 149. Maine 

 Agricultural Experiment Station. 1907. 



d Higgins, J. E. Marketing Hawaiian Fruits. Bulletin 4. Hawaii Agricul- 

 tural Experiment Station. 1907. 

 171 



