136 



at first, Imt after a few minutes ]ml)l)les began to be given off and a 

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

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

 thick 3^ellow slime, which perhaps conducted heat badly. 



In a second test, a similar potato culturt^ of ii-. phaseoli was exposed 

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

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

 of Ps. cmnpedTtH^ treated in the same way, behaved the same— there 

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

 w^ell for the behavior of tubes of Pa. eaiiq)c^trii< or Ph. 2jhaiieoU before 

 and after heating to H-o"^ C. 



As already shown, both Ps. phaseoJ! and I's. ca/npeMrisyfhen grown 

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

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

 potato culture of i^-. hyacinth! 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 HgO,^ 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 catalase.^ 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 gmmny substance 

 surrounding it. 



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

 away from the ])acterial 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 oidy to the bacteria themselves. Working in a 

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

 apochromatic, 1.40 n. ap., with 12 and 18 compensating, oculars, it has 

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

 ules lying betw^een the cells. In my opinion the color is lodged within 



1(1) Physiological Studies of Connecticut Leaf Tobacco. Deiiartinent of Agricul- 

 ture, Washington, D. C, 1900; (2) Catalase, a new en2ynie of general occurrence, 

 ■with special reference to the tobacco plant. Report No. 68, United States Depart- 

 ment of Agriculture, Washington, Government Printing Office, 1901, i)p. 47. 



