138 



(contaminated with H.,S).^ and nascent hydrogen. The loss of color 

 Avas most rapid in the carbon bisulphide, 30 to 60 minutes sufficing, in 

 some cases, to render the bright yellow bacterial slime as white as 

 white lead. On removing this fluid, which was neutral to litmus, luit 

 the vapor from which browned lead acetate paper, the A^ellow color 

 began to return in a few hours and linalh^ became nearly as bright as 

 before. The other substances reduced the color moi'e slowly, and on 

 their removal it was a much longer time in coming back, and never 

 became quite as bright a^ at lirst. The test with h^^drogen was made 

 as follows: The pigment was extracted by 23 days' exposure to c. p. 

 glj'cerin. Into this yellow glycerin was then thrown a small scrap 

 of zinc and some 30 per cent c. p. HCL. which caused a continual evo- 

 lution of gas. On the sixth day the yellow color was still visible; on 

 the seventh dav it was nearlv gone; on the tenth dav it was all gone. 

 On the thirteenth day the zinc was removed from the now colorless 

 fluid. The fluid remained colorless for some days (a week or two). 

 It then very gradually changed to yellow: 54 days after the removal 

 of the zinc it was still only feebly yellow. The yellow color was not 

 dissolved out by any of these reducing substances; at least no yellow 

 stain was imparted to the fluids. The bacteria were hardened by alco- 

 hol, ether, and chloroform into tough masses not easily divided. Simi- 

 lar masses remained soft under xylol, toluol, and turpentine, and had 

 an unctuous feeling when touched with a glass rod. Owing to the 

 hardening action of chloroform, the writer uses it in preference to 

 turpentine or xylol in passing the tissues from absolute alcohol into 

 paraffin. In sections cut therefrom the tissues of the host plant will 

 tear or become displaced more readily than the bacterial sheet. 



This pigment is slowly soluble in glycerol, as Wakker pointed out. 

 It is also soluble in water containing h^^drogen peroxide, in ethyl and 

 methyl alcohol, in acetic ether, and in acetone. The latter proved the 

 most ready and satisfactory soh'ent, most of the color being removed 

 in 30 to 60 minutes. Ethyl and methyl alcohol and ethyl acetate are 

 rather slow and feeble solvents. The color is slowh^ soluble, without 

 destruction, in strong ammonia water; it is quite soluble in water 

 saturated with ammonium carbonate. It is also soluble on long stand- 

 ing in glacial acetic acid. It is insoluble in petroleum ether. Jt was 



not dissolved or changed by remaining 30 days in ^ HCl. The color 



was not destro3^ed by steaming 25 minutes in water, nor by boiling in 

 strong ammonia water. It was not reduced by steaming in Avater con- 

 taining grape sugar! 



The acetone extract appears to be sensitive to light. On exposing 



'This is the carbon bisulphide which was used in my cx-perinients with Ps. rdm- 

 pestris (Centralb. f. Bakt., 2 Abt., Bd. Ill, page 479). 



