alkali enters, the neutral red will he -tained yellow. I 'lace in 11.40 

 Xa< ill. Ba(< '11 ' . ami Xll,< >ll. and reo.nl the time required for 

 the change of rlir to o^cur in each ca-e. As SOOn as the leat i> 

 \\h- 'lly \ello\\ place in pond water. hoe- the red o>lor return? 

 \\ Inch leave- have heen killed? 1 >oe- recovery of pmt. ipla>niic n>ta- 

 ur ? 



ij-. liiiperiiieahility to \a< 'II may he -h wn in a -inking man- 

 ner h\ the following experiment: I 'lace an Klodea leaf stained 

 in neutral red in n 40 Xll,< ill till yellow; then remove it to n 40 

 Xa< >11. h. ics it hcci>me red ? 



Stain 1'aramecia in a watch-gla-- of pond water to which 

 only a /><;<v of neutral red ha- heen added. Place a drop dcn-cly 



ude.l with red -tained I'aramecia in n 500 Xa')ll and 11/500 

 (XII,i<>H in pond water. XoU- the time of color change and 

 length of life in each ca-e. Are the I'aramoecia killed in Xa()II 

 hefiire the alkali enter-: How ahont Xll,()ll? Which region 

 of the cell HUM the Xa< >11 attack? 



U'(. c7i(/;;</r /;/ pcnnc(ih\l\t\ nil death. Place an Klodea leaf 

 -tained in neutral red in n 40 Xa< )|| and another, previously killed 

 h\ J minute- immer-ion in saturated chloroform water, in the 

 -ame -ohition. \\'hich i- more permeable? 



1^0. Place -mall cuhe-. cut from a heet and washed in running 

 \\ater, in a te-t-tuhe containing water. Place similar cuhe- washed 

 and then heated to hoiling for a moment in another test-tuhe of 

 water. Xote from time to time the amount of diffusion in each 



C, of the red pigment from the heet cuhe>. Significance? 



i _} i . The rapid penetration of Xll,< HI into cells is probably to 

 he correlated with it- solnhility in fat solvents or Hpoid substances. 

 Suluhiliu of XII,' )!I in fat solvents max he demonstrated as 

 follow-: Shake a \\lol -olmion of lecithin with egg alhumin solution 

 coiiiaining a fi-w <lrop- of neutral red. Xote that the glohule- of 

 lieii/ol taki- up the neutral red. X'o\\- place -ome of the latter in 

 n IH) Xll,()|| and n too Xa< >l I in watch-gla--i--. Which alkali 

 penetrate- and \\liy? 



132. Sll/ill and Xa<>ll diffuse through dead memhranes at 



the -ame rate, hem n-trale thi- hy o>\-ering the end- of two tuhe- 



uith a e. -llodion film (made on mercury -urface and tied tightly 



the tuhe-i. then tilling with agar-agar colored \\Jth neutral red 



and immersing the covered end of the tuhes in n loo Xll,<)ll and 



v,"a<ll re-].e< ii\el\. Tlu- diffu-ion rate- of Xa<>|| and Xll,(>ll 



in pure \\ater are ].racticall\ the -ame. 



