32 CELL-CONTENTS AND CELL-WALLS. 



Half fill a wash-bottle with water, add a few drops of 

 chloroform about 1 per cent. cork tightly, and shake 

 the bottle. Fix a rubber tube to the short tube of the 

 bottle and to one end of the gas-chamber ; join the other 

 end of the chamber by rubber tubing to an aspirator, and 

 let the air charged with the chloroform pass through the 

 chamber, on which is inverted a cover-glass with a drop 

 of water containing an Elodea leaf or other object showing 

 active protoplasmic streaming. The chloroform vapour 

 causes the movement to slow down and finally stop. Dis- 

 connect the wash-bottle, so as to let fresh air pass through ; 

 the movement will be resumed if the chloroform vapour 

 has not been allowed to kill the protoplasm. 



34. Effect of Carbon Dioxide. Lead carbon dioxide 

 through the gas-chamber e.g. by placing plain water in 

 the wash-bottle and joining its long tube to a bottle in 

 which carbon dioxide is generated by pouring dilute 

 hydrochloric acid on marble chips or chalk. The move- 

 ment is quickly arrested, but is renewed on disconnecting 

 the apparatus to let fresh air pass through. 



35. Effect of Exclusion of Oxygen. Eepeat the pre- 

 ceding experiment, using hydrogen generated by pouring 

 hydrochloric acid on zinc filings. Or oxygen may be ex- 

 cluded by simply placing with a pipette some freshly made 

 potassium pyrogallate in the gas-chamber, after sealing 

 the tubes up, and quickly laying the inverted cover-glass 

 preparation on the upper edge of the chamber. In absence 

 of oxygen the movement continues longer than in the 

 preceding experiments and is only gradually slowed down ; 

 if hydrogen is used, it acts by simply excluding oxygen 

 from the protoplasm, not as a poison or narcotic. 



III. EFFECTS OF HEAT, COLD, ETC., ON PROTOPLASM. 



36. Effects of Heat, Cold, Poisons, etc., on Proto- 

 plasm. We have already noted the effect of these 

 agencies on protoplasmic streaming. That protoplasm 

 alters when killed can be shown in various ways. 



