136 



at first, but after a few minutes bubbles began to be given otf and a 

 small amount of froth collected, but not over one five-hundredth as 

 much as from the unheated tube. This tube was, of course, full of a 

 thick yellow slime, which perhaps conducted heat badly. 



In a second test, a similar potato culture of Pf>. pJiaseoli was exposed 

 for 2 hours at 85^ C. On then adding H.,Oo there was no evolution 

 of gas either immediately or after a time. A similar potato culture 

 of Ps. camjpestris. treated in the same way. behaved the same — there 

 was no evolution of gas. The above illustration would serve equally 

 well for the behaA'ior of tubes of P><. cainptsfrfs or Ps. 2>hai<toll before 

 and after heating to 85^ C. 



As already shown, both Ps. j^haseol! and Ps. ar/npest?' isy^hen grown 

 on potato produce an abundance of diastase, but the breaking up of the 

 H2O3 with liberation of oxygen can hardly be due to that enzyme, for a 

 potato culture of Ps. liyacinthi of the same age as the preceding gave 

 an enormous quantity of gas. although, as usual, it had made a rather 

 meager growth (owing to its feeble diastasic action). This potato gave 

 a strong starch reaction with iodine potassium iodide. Stearns &. Co. 's 

 pancreatic diastase also failed to cause any evolution of gas when it was 

 dissolved in water and HjO., added. 



Dr. Oscar Loew has given reasons for believing that this decompo- 

 sition of hydrogen peroxide is due to a hitherto unsuspected oxidizing 

 enzyme, which he has named cataJa.'^t^ and which he believes to be 

 universally distributed in plants and animals and to have to do with 

 respiration. 



PIGMENT STUDIES. 



The Yellow Color. 



Dr. Wakker appears to have been uncertain whether the yellow color 

 was inherent in the organism itself or only in a gummy substance 

 surrounding it. 



The yellow color of Ps. hyaehithi can not be shaken loose or filtered 

 away from the bacterial cells by water, and, with the exception of 

 nutrient starch jelly containing glycerine, it was never imparted to 

 any of my fluid or solid culture media, whether neutral, acid, or alka- 

 line. It pertains only to the bacteria themselves. Working in a 

 good light with the best appliances at my disposal, viz. Zeiss 2 mm. 

 apochromatic, l.ttO n. ap., with V2 and 18 compensating oculars, it has 

 never been possible to locate the yellow pigment in any gum or gran- 

 ules lying between the cells. In my opinion the color is lodged tcithin 



^ (1) Physiological Studies of Connecticut Leaf Tobacn). Department of Agricul- 

 ture, Washington, D. C, 1900; (2) Catalase, a new enzyme of general occurrence, 

 with special reference to the tobacco plant. Report No. 68, United States ])epart- 

 ment of Agriculture, AVashington, Government Printing Office, 1901, pp. 47. 



